GENERAL PRINCIPLES .

Densified Systems containing homogenously arranged ultrafine Particles , for brevity termed DSP in the following specification and claims , were described and defined in detail for the first time in

International Patent Application No . PCT/DK79/00047. The present invention relates to important further developments of the DSP systems , including new types of DSP systems and new materials within previously described types of DSP systems , new techniques for establishing DSP systems , and new applications of DSP systems .

DSP systems give rise to hitherto unattainable mechanical .qualities, including strength, density, and durability, of materials and ar¬ ticles based on such systems and make it possible to establish such articles and materials by advantageous novel methods which broaden the possibilities of establishing advanced microstructures of constructional materials for a great variety of applications .

In a very brief form, the basic principle of DSP systems comprises placing ultrafine bodies or particles having a size of from about

50 A to about 0.5 μm in homogeneous arrangement in the voids between substantially densely packed bodies or particles having a size of from about 0.5 μm to about 100 μm and being at least one order of magnitude (power of 10) larger than the respective ultra- fine particles . Some essential characteristics of the DSP systems are contained in the following five points :

l .- DSP systems utilize known geometric and kinematic principles for mutual arrangement of bodies , especially particles , in desired configuration - in particular in very dense arrangement - in sy¬ stems of fine particles or bodies which are 1 - 2 orders of magni¬ tude finer than the systems in which it has so far been possible to benefit from known particle geometry strategy . The DSP systems

overcome the locking surface forces between adjacent bodies which hitherto have prevented bodies or particles of colloid size from being arranged in a desired dense configuration .

2. In spite of the fine bodies or particles involved in the DSP systems , DSP materials may be shaped in a substantially low stress field. This has been made possible by advanced utilization of dispersing agents (e. g. , in the cement system, by use of a large amount (1 - 4% by weight of a concrete superplasticizer which is up to one order of magnitude more than what was used in the known art) .

3. In the DSP materials, strength and durability are very much increased. In addition to this, mechanical fixation of reinforcing bodies, e. g. fine incorporated fibers , is increased even more than the strength, the increase being one or several orders of magni¬ tude. This is due to the fact that the dimensions of roughness and wave configuration on the reinforcing bodies which are necessary for obtaining "mechanical locking" of the reinforcing bodies in the matrix, are lowered by 1 - 2 orders of magnitude. This makes it possible to obtain "mechanical locking" of fibers which are one to two orders of magnitude finer than the fibers which could hitherto be "mechanically locked" .

4. According to an aspect of the present invention, the quality

(primarily strength and rigidity) of the DSP materials may be further increased by incorporating very strong additional particles (e.g. , sand and stone of refractory grade bauxite for incorpo¬ ration in Portland cement-based DSP materials) .

5. Typical DSP materials are materials which may be shaped from a mass with plastic to low viscous consistency by simple shear de¬ formation without any exchange of material with the environments , which means that no liquid will be or has to be moved or squeezed out of the mass during the formation of the dense structure. This makes it possible to prepare high quality products of much more complicated shape and larger size than hitherto - and makes it possible to obtain anchoring of components , especially reinforcing

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bodies of any kind, which could not satisfactorily (or which could not at all) be introduced in corresponding high quality matrices prepared in the traditional manner. This aspect of the DSP mate¬ rials also opens the possibility of new and more advantageous production techniques for known articles .

In the present context, the terms "bodies" and "particles" refer to domains with physical boundaries , the term "physical" referring to specific properties , e . g. , mechanical, electrical, optical, or che- ical properties .

STRUCTURE OF THE DSP MATRIX.

Shaped articles comprising a DSP matrix may be defined in general as shaped articles comprising a coherent matrix,

the matrix comprising

A) homogeneously arranged bodies or particles of a size of from about 50 A to about 0.5 μm, or a coherent structure formed from such homogeneously arranged bodies or particles , and

B) densely packed bodies or particles having a size of the order of 0.5 - 100 μm and being at least one order of mag¬ nitude larger than the respective particles stated under A) , or a coherent structure formed from such densely packed particles ,

the bodies or particles A) or the coherent structure formed therefrom being homogeneously distributed in the void volume between the bodies or particles B) ,

the dense packing being substantially a packing correspon¬ ding to the one obtainable by gentle mechanical influence on a system of geometrically equally shaped large bodies or par¬ ticles in which locking surface forces do not have any signi¬ ficant effect,

and an inter-particle substance (I) in the space between the bodies or particles A and B or the structure formed by the bodies or particles A and B .

The bodies or particles A and B are typically solid bodies or par¬ ticles , but they may also be gas phase or liquid phase bodies or particles . Likewise, the inter- particle substance I may be solid, or it may be a gas phase or liquid phase substance, provided that when the inter-particle substance in a shaped DSP article is not solid, the necessary "gluing" to retain the shape of the article is provided by particle-to-particle bonding.

Thus, the substantially coherent structure of the matrix of the above-defined DSP articles of the may be due to the homogeneous¬ ly arranged or densely packed bodies or particles A being com¬ bined with each other to form a coherent structure, or due to solid particles B as stated above being combined with each other to form a substantially coherent structure, or both the ultra fine particles A and the particles B in the shaped articles may each be combined with each other to form coherent structures , and/or particles A being combined with particles B to form the coherent structure. The combination between the particles A or between the particles B or between particles A and/or particles B may be of any character which results in a coherent structure. In systems comprising cement particles as particles B and silica dust particles (as defined below) as particles A the coherent structure is formed due to partial dissolution of the solid particles in the aqueous suspension from which the articles are made, chemical reaction in the solution, and precipitation of the reaction product, the silica dust being less reactive in this regard than the cement. In this connection it is noted that depending on the idendity of the par-

tides A and B , also other mechanisms imparting coherence may have been responsible for the coherence of the matrix, such as melting or sintering, etc . The chemical reaction mentioned above may be one which takes place between the particles A or their dissolved constituents , or between the particles B or their dis¬ solved constituents , or between particles A and B or between constituents of particles A and particles B .

A substantially coherent structure may also be established by solidification of other inter-particle substance, e . g. , by solidifi¬ cation of a melt or liquid, such as physical solidification, including solidification of a metal or glass melt, and chemical solidification, including polymerisation, e . g. to form a plastics substance .

Shaped articles comprising a matrix having a substantially coherent structure comprising homogeneously arranged or densety packed particles A together with densely packed particles of Portland cement were obtainable in the known art only by compaction in a high stress field, typically by high pressure powder compaction . Hence, one very interesting class of shaped DSP articles comprises shaped articles produced by shaping in a low stress field of less than 5 kg/cm 2 , preferably less than 100 g/cm 2 , and having a matrix of a substantially coherent structure comprising homogene¬ ously arranged or densely packed particles A or a coherent struc- ture formed from such homogeneously arranged or densely packed particles A, and densely packed particles B , at least 20% by weight of the densely packed particles B being Portland cement particles , or a coherent structure formed from such densely packed par¬ ticles B . Another way of defining the class of shaped DSP articles having homogeneous arrangement of particles A between densely packed particles B of which at least 20% by weight are Portland cement particles is by referring to the dimensions of the article . Such articles having a correspondingly dense packing between the particles B and having at least one dimension of at least 1 m and a minimum cross section of at least 0.1 m are not believed to have been made in practice, prior to the invention of the DSP systems , by high pressure powder compaction technique . Another vay of expressing this kind of DSP article is by defining that the articles

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have a complex shape that does not permit its establishment throug powder compaction. Finally, when the particles B have a molecular structure different from the particles A, such as will most often be the case in practice, such structures in which at least 20% by weight of particles B are Portland cement and which otherwise comply with the definition stated above, could not have been made using traditional techniques irrespective of the size or shape of the structures . While it may have been possible in powder com¬ paction techniques to obtain a combination of the two systems comprising homogeneously arranged or densely packed particles A and densely packed particles B, this would have involved crushing of the larger particles during the compaction process to result in the smaller particles and hence, would have meant that the larger particles and the smaller particles would have identical molecular structure .

One very interesting feature of the DSP materials is that it is possible to establish structures of the types discussed above with inherently weak particles and inherently weak additional bodies which would have lost their geometric identity (would have been crushed or drastically deformed) by the known art treatment in a high stress field. This makes it possible to establish dense struc¬ tures with materials not previously available therefor.

In most cases , the most valuable strength properties are obtainable when both particles A and particles B are densely packed. This situation is illustrated in Fig. 1 in International Patent Application No . PCT/DK79/00047 which shows the principles of the geometrical arrangement involving dense packing in fresh DSP paste consisting of Portland cement particles and ultra fine particles between the

Portland cement particles . With reference to tests made with mor¬ tar, fiber-reinforced paste and concrete based on this novel matrix, the Portland cement particles (average dimension 10 μm) were arranged in a dense packing corresponding to a volume fraction of cement (volume of Portland cement divided by total volume) of

0.43 - 0.52. If ordinary cement paste - not containing ultra fine particles - had been arranged in the same dense packing, it would correspond to a water/cement weight ratio of 0.42 to 0.30. This

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would normally be claimed to be densely packed. In the DSP material, it has been found possible to incorporate further up to

50% by volume of ultra fine solid particles in voids between the cement particles . The solid incorporated was fairly densely packed extremely fine spherical silica particles with an average diameter of

2 0.1 μm and a specific surface of about 250,000 cm /g. The total volume fraction of solid in the matrix of cement plus silica dust amounted to 0.64 - 0.70. The water/solid ratio (by weight) was

0.188 to 0.133.

The amount of silica dust to secure a dense packing of the silica dust particles depends on the grain size distribution of the silica dust and, to a large extent, on the void available between the densely packed particles B . Thus , a well-graded Portland cement containing additionally 30% of fine spherically shaped fly ash particles will leave a much smaller available void for the silica dust when densely packed than correspondingly densily packed cement in which the grains are of equal size. In systems in which the particles B are mainly Portland cement, dense packing of silica dust would most likely correspond to silica dust volumes from 15 to

50% by volume of particles A + particles B . Similar considerations apply to systems comprising other types of particles or bodies A and B .

The principles of dense packing are dealt with in detail in the following section "PRINCIPLES OF DENSE PACKING" .

In the present specification and claims , the terms "ultra fine silica particles" and "silica dust" are intended to designate SiO~-rich particles having a specific surface of about 50, 000 - 2,000,000 cm 2 /g, especially about 250,000 cm 2 /g. Such a product is pro¬ duced as a by-product in the production of silicium metal or ferrosilicium in electrical furnaces and comprises particles in a particle-size range from about 50 A to about 0.5 μm, typically in the range from about 200 A to about 0.5 μm .

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Dense packing of extremely fine powders according to. the DSP principles has , for example, been realized in concrete (Example 1) , mortar (Examples 3 and 9 in International Patent Application No. PCT/DK79/00047) , and thin extruded panels with a reinforce- ment of plastic fibers (Example 2 in International Patent Appli¬ cation No . PCT/DK79/00047) . In these cases , the binder matrix was prepared from Portland cement (specific surface about 2400 -

2 4400 cm /g) and ultra fine spherical silica dust (specific surface

2 250,000 cm /g) arranged in an extremely dense packing (water/ powder weight ratio 0.18 and 0.13, respectively) by using, as dispersing agent, a concrete superplasticizer in an extremely high amount (1 - 4% by weight, in particular 2 - 3% by weight, of superplasticizer dry matter, calculated on the cement plus the silica dust) .

The concrete was prepared from an easily flowable mass and had a high strength (the compressive strength of water-cured, wet cylindrical test specimens with diameter 10 cm and height 20 cm was 124.6 MPa after 28 days and 146.2 MPa after 169 days) . The strength is 20% higher than the highest corresponding strength values reported for concrete made and cast in the normal way, including the use of superplasticizing additives (vide Example 1 in International Patent Application No . PCT/DK79/00047) . The com¬ pressive strength of mortar prepared from an easily flowable mass and cured in water for 4 days at about 60° C was as high as 179

MPa, as assessed by tests on wet specimens having a diameter of 10 cm and a height of 20 cm (vide Example 9 in International Patent Application No . PCT/DK79/00047) .

BODIES OR PARTICLES A AND B OF THE DSP MATERIALS ,

In ^" International Patent Application No . PCT/DK79/00047 , the particles A and B of the DSP materials are, in general terms , characterized as solid particles having particles sizes typically between, 50 A and 0.5 μm and 0.5 μm and 100 μm, respectively.

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The said international patent application mainly discloses compact- shaped particles , typically relatively hard materials such as Port¬ land cement, lime, fly ash, and colloid silica. However, also weak

2 mmaatteerriiaallss eeaassiillyy ddeeffoorrmmaabblle under stress of below 5 kg/cm are mentioned as particles B .

According to the present invention, the particles A and B may be of any shape, a typical useful shape being elongated rod-like shapes where the minimum dimensons are typically between 50 A and 0.5 μm for the particles A and 0.5 - 100 μm for the par¬ ticles B . The length of the particles may be of arbitrary size larger than the transverse dimensions , such particles typically being chopped fibers or whiskers having a length/diameter ratio from 1000 : 1 to 5 : 1, or continuous fibers such as wires .

In the present specification, the term "bodies" designates bodies of any of the above-mentioned possible shapes, including particle shape, elongated shape, plate shape, or fiber or continuous fiber or wire shape,, and the term "particles" generally designate com- pact-shaped particles , but may also encompass angular particles and somewhat flattened out or elongated shapes within the normal understanding of the definition scope of the term "particles" . Furthermore, in connection with the general description of DSP systems in the present specification, the term "particles" may be used as a common designation instead of "bodies" where the meaning is evident.

The dense packing as discussed in the section "PRINCIPLES OF DENSE PACKING" is related to the geometry of the particles and the type of packing or shaping process . Thus , with simple mixing or casting technique, a volume concentration of 10% of elongated bodies B ma ⁷ - often be considered high and will constitute dense packing when the mixing or casting technique according to which the DSP materials containing such bodies have been established is a simple mixing or casting technique, whereas the corresponding volume concentration with parallel arrangement of fibers B in filament winding may be as high as 40 - 70%.

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As indicated above, the bodies may also be plate-shaped, typically having thicknesses of 50 A to 0.5 μm for the particles A and 0.5 μm to 100 μm for the particles B .

According to the present invention, the bodies or particles A and

B may be of any chemical composition .

The particles B may consist of solid material such as described in International Patent Application No . PCT/DK79/00047, but as stated above, they may also, according to a novel feature of the present invention, be liquid or gaseous .

Gas phase particles B are typically present in very fine porous foam structures with walls constituted by solidifed particle A-based material.

Liquid phase particles B are also typically of interest in a kind of fine foam with liquid-filled interior, also with walls constituted by solidified particle A-based material.

One type of especially interesting bodies or particles B are elon¬ gated particles or fibers and whiskers of ultra high strength, e. g. metal fibers or whiskers , carbon fibers, boron fibers, glass fi¬ bers, l ₂ O„ whiskers , silicon carbide whiskers , graphite whiskers , Kevlar fibers , high strength polypropylene fibers , wollastonite , and asbestos .

The bodies or particles A of the DSP materials may serve a wide variety of purposes :

1. They may function as building stones which are "glued" together to confer strength and rigidity to the material.

For this purpose, the material of which the particles consist should have chemical affinity to the "glue" formed . (This is obtained by selecting particles A having a suitable chemical structure and/or by suitable surface treatment of the par¬ ticles) .

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2. The bodies A may also function to confer toughness to the DSP material to avoid ultramicro cracks .

For this purpose, the bodies A are suitably fibers , e . g. , of a diameter between 0.5 μm and 50 A and a length between 100 μm and 500 A, preferably a length between 10 μm and 500 A, preferably together with compact particles A, perfectly in combination with compact particles A in a high concentra¬ tion . Examples of suitable elongated bodies or fibers A for this purpose are ultrafine fibers , whiskers and needle-shaped crystals .

3. The bodies A may also function to actively contribute to the formation of the "glue" , e.g. , where the particles A are particles which establish a solid structure by partial disso¬ lution in inter-particle water and chemical reaction in the water phase with precipitation of a reaction product, or where particles or fibers A are of a metal which is subjected to melting- solidification or sintering in a separate subsequent step after the initial formation of the DSP matrix.

4. The bodies A may act as an accelerator or a catalyst for desired chemical processes proceeding in the DSP system . Thus, e. g. , particles A may consist of ultrafine cement to accelerate the hardening of cement based DSP systems , typically cement/silica dust/concrete superplasticizer DSP systems .

5. The particles A may be active as scavengers :

i) against corrosion, ϋ) against alkali reactions , e. g. , when the particles A consist of SiO ₂ ) ϋi) to protect plastics fibers , the particles A may be opaque to ultraviolet radiation (and may preferably function as oxygen scavengers) , iv) as toxins or poisons active against biological deterioration, in particular microbial deterioration,

v) as active ingredients for reducing soluble chromate content of cement (such as thiosulphate or ferrosulphate) vi) as scavengers which function by ion exchange to scavenge ions from liquids leaching through the structure such as sca- vengers absorbing radioactive ions from radioactive matter contained in a DSP matrix material, vϋ) as hydrogen rich and/or heavy elements to protect against radioactive irradiation and X-rays (e. g. heavy components such as lead particles) .

5. The particles A may function to confer optical properties , including reflection properties and transmission properties and fluorescence properties .

For this purpose, the particles A may be pigments which are adapted in size according to desired optical properties, in which connection sizes below 0.5 μm are very effective .

6. The bodies A may be used for conferring desired electrical properties (e. g. to confer ion conductivity) .

7. The bodies A may be utilized as electrically conductive elements .

8. The bodies A may be incorporated as components with specific dielectrical properties .

9. The bodies A may be magnetic particles .

10. The bodies A may be used to confer particular chemical and thermal properties :

- . i) where chemical or thermal resistance is desired, or ϋ) where chemical or thermal resistance should be as low as possible (e. g. , to obtain a microfine structure by subjecting a DSP matrix containing chemically or thermally easily remov¬ able bodies A to corrosive influence or combustion to remove

the bodies A, resulting, for example, in a dense strong DSP matrix with ultrafine pores or holes throughout the structure) .

11. The bodies A may be of hard materials to obtain abrasion 5 resistance of the DSP material.

PRINCIPLES OF DENSE PACKING.

10 Dense packing of bodies and particles is essential in connection with DSP systems . As an example, the essential feature of Portland cement-based DSP materials is dense packing of cement particles , combined with the incorporation of ultrafine particles in the voids between the cement particles .

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In connection with the creation of volumetrically stable DSP con¬ crete and mortar, it is also desirable to pack sand and stone as tightly as possible, with the spaces between the aggregates filled as tightly as possible with dense DSP paste .

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This packing is not uniquely defined, but depends on the shape of the bodies or particles in question, on the size distribution, and on the method of compaction .

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Effect of Particle Shape.

The packing density depends on the particle shape, so that the more angular, oblong, and rougher the particles, the lower will be 30 the density.

In connection with Portland cement DSP paste, the large particles (cement) will typically have a cubicle-angular shape, with moderate packing capacity. (The shape of cement particles depends on the 35 production method (grinding) . From the point of view of packing, spherical cement would be ideal. Such cement could be produced by nucleation and growth in liquid phase . ) The ultrafine powder,

on the other hand, consistes of sphericals formed by condensation from gaseous or liquid phase. The spherical shape results in ideal packing properties .

Densely packed elongated bodies, such as fibers , will typically be arranged in a much more open structure than compact- shaped particles (vide Fig. 4) unless special precautions are taken (vide Fig. 5) .

Effect of Particle Size Distribution .

The effect of the particle size distribution can be illustrated by discussing binary mixes (large particles and small particles) as opposed to multi-component mixes .

Dense packing of particles dominated by the geometry of the par¬ ticles (without influence from surface forces) has been treated worldwide in the literature dealing with particulate technology in various fields , for example in "Particulate Technology, Clyde Orr, Jr. 1966, The MacMillan Company, New York, and "Principles of

Particulate Mechanics" , Brown and Richards, 1970, Pergamon Press . It is characteristic that packing of particle systems in which sur¬ face forces are insignificant is independent of the absolute particle size and depends only on the shape of the particles, the relative size distribution, and the mechanical way in which the particles are placed. This means that regular packing of equal spheres results in the same volume fraction of solids content (for example, 0.52 for cubic packing and 0.74 for hexagonal packing) irrespec¬ tive of the absolute size of the spheres . The density of the packing is strongly influenced by the relative particle size distribution, that is , the ratio between the various particle sizes . Thus , Brown and Richards (loc. cit. ) report classical experiments with binary packings of spherical particles with various size ratios where the volume fraction of solids content increases from about 0.63 for packing of each of the individual particle size fractions to 0.70 for a mixture of large and small particles with a size ratio of 3.4: 1 and to 0.84 for a mixture of large and small particles in a size

ratio ^" of 16 : 1. The density of the packing is also strongly influ¬ enced by the mechanical compaction method. Simple pressure compaction will normally not lead to very dense packing of particle systems in which the particles retain their geometric identity (that is, are not crushed or heavily deformed) . Normally, denser packing is obtained by shear deformation, repeated shear deformation, or balanced vibration, all with application of a small normal pressure to secure that the repeated deformation finally results in a more dense structure . For this reason, it is not possible to state dense packing in terms of one unique quantity . The "dense packing" referred to in the present specification is to be understood as substantially such a dense packing which would be obtained in systems without locking surfaces by influences of the above types such as shear deformation and balanced vibration .

The densest packing is obtained with a high ratio between large and small particles , typically in excess of 20.

For small diameter ratios, the maximum packing density is reduced because of the wall and barrier effect (vide Figs . 37 and 43) which gains increasing importance with increasing ratio of fine particles to coarse particles .

Without the wall and barrier effect, 100% dense packing could be achieved in multi- component mixed by continuously filling the spaces between the particles with fiber particles .

In practice, where the ratio between largest and smallest particles is limited, for example to about 10 4 - 105 for concrete or cement- based DSP with up to 10 mm aggregate and fine cement fraction of

1 μm, and for the DSP, also ultrafine silica particles having a mean particle size of about 0.1 μm, a marked wall effect and barrier effeGt would occur if the number of discrete particle fractions were more than 3 or 4, which would result in a far from ideal packing.

There seems to be no theory that enables the drawing-board de¬ sign of the grading curve that will give optimum packing. Hence,

the solution seems to be a compromise between a few-component packing with little wall effect and barrier effect, on the one hand, and multi- component packings , on the other hand. In each par¬ ticular case, the optimum packing may be assessed by preliminary physical compaction tests .

However, some general principles may usually be utilized:

1. A densely packed particle fraction - for example, rounded, compact- shaped fine particles between 10 and 20 μm, should be protected against dilution by ensuring a considerable gap in particle size (for both larger and smaller sizes) .

2. For ultra-strong cement-based materials, the dense packing of the strength- delivering cement particles should be protected by gap in the particle size (for both larger and smaller sizes) , e . g. , by using on the one hand a relatively coarse sand and on the other hand ultrafine particles that are considerably finer than the finest fractions of the cement.

3. Where other particles or fibers of cement fineness , e.g. , 10 - 20 μm diameter glass fibers - are used in cement-based DSP, it is possible to compensate for the relatively high dilution of the cement fraction which takes place at the surface of these particles or fibers by adding a correspondingly higher pro¬ portion of ultrafine particles A

The dense packing of bodies or particles where surface forces are eliminated is strongly dependent on the kinematics of the arrange¬ ment of the bodies . For example, fibers may be arranged in what is considered dense packing in the context of the present appli¬ cation by 1) a simple mixing and casting process (vide Fig. 4) , 2) sedimentation (vide Fig. 48) , and 3) filament winding as illustrated in Fig. 5. The density or fiber concentration is strongly in¬ creasing from 1) via 2) to 3) . Typical fiber concentration values obtainable by the three methods are 5, 20, and 60 per cent by volume , respectively .

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Thus , it will be understood that the dense packing is the combined effect of the particle or body shape and the way the particles or bodies have been arranged, that is , the kinematics , under con¬ ditions where the particle or body concentration is insignificantly influenced by surface forces such as in the DSP systems with effective dispersing agent incorporated.

OVERCOMING SURFACE FORCES.

An essential part of the establishment of a DSP system is the overcoming of surface forces between the small particles and bodies to secure the important dense packing.

For cement-based DSP, the question of obtaining dense particle packing is, thus, essentiall3 ^r a question of overcoming locking surface forces between the cement particles and the ultrafine par¬ ticles in aqueous dispersion .

For particles of compact, rounded shape, held together by surface forces , the forces required to separate two particle in point con¬ tact or to perform mutual sliding are proportional to the particle dimension (d) and the surface tension (γ)

F a γd

The surface tension γ is defined as 1) the surface tension between the liquid meniscus and surrounding fluid (usually air) when cohe¬ sion is caused by the meniscus or 2) the work required to create one unit area of new surface by removing plane-parallel faces from the contact area to infinite distance.

On the assumption that separation and sliding resistance dominate over rolling resistance, the yield stress of a powder (which is proportional to the force acting on a particle, divided by the area of the particle) can be written

SLi

Yd

or, in dimensionless form,

2d = constant Y

where the constant is a function of the geometry of the particulate system (relative particle size, shape and arrangement) .

This qualitative model has played a great role in the choice of strategy for the production of dense, strong, cement-bound materials, including DSP, where depiction of the particle packing as a function or 2— has been used .

The quantity ^— is a measure of the extent to which external stresses (p) are able to overcome internal cohesion (4) .

Ultra-fine particles subjected to surface forces are typically packed in a- very open structure if the packing takes place under moderate external pressure . This is a case of compaction of a particulate system with very low, dimensionless compaction pressure ^■ —, resulting in a correspondingly low particle concentration .

Denser packing can be achieved by 1) heavier compaction, 2) reduction of surface forces , for example by means of surface-active agents , or 3) selection of larger particles .

For very high values of £ *—d, the effect of surface forces is practi-

Y cally overcome, cf . , for example, a pile of stones . Here , the particle packing is principally a question of particle geometry, particle friction and the way in which the compaction is made, i. e . by vibration.

The production of extremely strong and dense concrete requires a

binder of very fine particles arranged in dense packing. However, in normal circumstances , the combination of small particles , locking surface forces and moderate compaction load does not permit the production of such a dense structure.

According to the DSP principle, the locking effect of surface forces in cement-based materials is practically completely eliminated by means of dispersing agents , thereby enabling ideal geometrical arrangements with packing of small, spherical particles between larger particles to ensure a very dense structure despite the fact that the small particles packed between the cement particles are about 1/lOOth the size of normal cement particles (silica dust with an average diameter of 0, 1 μm) .

Thus , according to the DSP principle, efficient dispersing agents are utilized to change the ultra-fine particle-based materials into a condition where the packing density has become purely a geome¬ trical and kinematic problem, known from the theory of packing of large- size particles .

According to a particular aspect of the present invention, it is also possible to perform compaction of the DSP articles in higher stress fields , cf . the following section "SHAPING IN A HIGH STRESS FIELD" . Utilizing compaction in high stress fields , it is possible to successfully establish DSP systems based on the smallest particle size in the range stated for particles A, that is 50 - 200 A, where surface forces (γ) according to the model

* — = constant

will have increasing importance. By increasing the compaction stress p accordingly, the high level of

_ά Y

which is characteristic of the condition where surface forces have been overcome, can be retained.

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For other methods of arranging fine bodies or particles , such as sedimentation, similar principles may be utilized, only the mathe¬ matical models being different. Thus , the dense arrangement by sedimentation of small fibers is dependent upon whether the force of gravity acting on the fiber is able to overcome the surface forces which tend to fix or lock the sedimenting fiber (such locking or fixation is typically a fixation in an absolutely un- desired position unparallel to other fibers) so that the sedimenting fiber will obtain a desired position substantially parallel to already sedimented fibers (vide Fig. 48) .

FUNCTION OF DISPERSING AGENT IN PORTLAND CEMENT/ULTRA FINE PARTICLE SYSTEMS .

The dispersion of fine particles by use of surface active agents is well explained in general terms in the literature on colloidal and surface science.

The purpose of using a surface active agent is to establish such repulsive forces against adjacent particles that the repulsive forces become able to overcome the mutual attraction caused by London/ van der Waals forces and possibly other attraction forces . By this measure, it is attempted to eliminate blocking between the particles, thus ensuring the sliding of the particles relative to each other which is absolutely essential for the establishment of dense packing in a low stress field.

According to classical theory, two repulsive mechanisms are normall considered: electrical repulsion caused by generation of electrical diffuse double layer in the medium surrounding the particles (cf. the D .L.V.O. theory) , and steric hindrance where particles are prevented from coming together (e . g. prevented from flocculation) due -to the presence of adsorbed layers of another compound on their surface .

Such adsorbed layers may be molecules from the medium, or they r a.y be surfactant molecules . The physical interaction of the ad-

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sorbed molecules as the particles approach each other acts as a barrier to flocculation. It is believed that steric hindrance effect is the dominant factor in cement dispersed in water under the in¬ fluence of typical concrete superplasticizers , but that also elec- trical repulsion enter into the mechanism as an extra contribution .

Experience over many years indicates that a pure electrical repul¬ sion effect is insufficient to prevent flocculation of Portland cement in water (probably due to a high concentration of divalent, tri- valent counterion (Ca and Al ) which, according to the Hardy-

Schultz rule, compresses the difused double layer, and perhaps also due to formation of direct chemical bonds (or bridges) . It seems likely that an efficient dispersion of ordinary Portland cement in water is strongly dependent on dispersing agents securing efficient steric hindrance.

Achievement of a good dispersion of ultra fine silica, e . g. having an average size of 0.1 μm, in water is basically much simpler than the achievement of a similar dispersion of the much coarser Port- land cement (typically with average particle size of 10 μm) .

Thus , an efficient dispersion of colloid silica in water (without salt content) is obtained by pH control (pH typically above 7 or 8) is reported in Surface and Colloid Science, editor Egon Matijeviec, Ralph K. Her, 1973, John Wiley & Sons) . Practical experimental experience with the fine silica dust used in the working examples

2 (specific surface area about 250.000 cm /g) demonstrates the same general behaviour.

Thus , 1 : 1 mixture of silica dust and tap water (by weight) and a

2: 1 mixture of silica and 3% sodium tripolyphosphate aqueous so¬ lution both result in slurries with moderate viscosity which are easily mixed in low shear mixers or by hand. However, attempts to combine such silica/water systems with Portland cement result in a pronounced flocculation .

Thus , the addition of a small amount of easily flowable Portland

cement/water slurry (typically a water: cement ratio of 1) to a large batch of silica/water slurry of the types and concentrations mentioned above (e.g. typically 1 part of cement slurry to 10 parts of silica/water slurry) results in a drastic stiffening which renders any further mixing impossible.

This demonstrates that the solutes in the water generating from the cement destroy the dispersion of the ultra fine silica particles . The precise mechanism of bond formation between the silica par- tides is not known, but the explanation is likely to be along the lines of reduced double layer repulsion and formation of various types of direct bonds or bridges .

By the use of concrete superplasticizers, such as sodium salt of a highly condensed naphthalene sulphonic acid/formaldehyde conden¬ sate, of which typically more than 70% consist of molecules con¬ taining 7 or more naphthalene nuclei, it is easy to obtain an extremely good dispersion of the combined ultra fine silica/Portland cement/water system, making the dense packing of the binder possible in a low stress field.

Hence, the succes of superplasticizers in ultra fine particle/cement/ water DSP systems is not due to their ability to disperse ultra fine particles in water (indeed, other surfactants are even better for this purpose) , but due to the fact that they are able to provide a good dispersion of the silica in the specific Portland cement/water environment.

STRUCTURE AND PROPERTIES OF COMPOSITE MATERIAL

The present invention provides several novel methods and principle for establishing DSP materials which are discussed in separate sections in the following. The present section deals, in particular, with the establishment of ultra strong cement-based DSP materials .

The strength of ordinary concrete depends primarily on the quality

of the cement binder which binds together sand and stone, and only to a smaller degree on the quality of the sand and stone as long as normal sound materials are concerned.

The reason for this is that the binder is the weak link in normal concrete and that ruptures predominantly occur through the binder, without passing the sand and stone particles .

In textbooks on concrete design, this is clearly expressed by assuming, as a first approximation, that the strength is a function solely of the composition of the binder (expressed as the cement concentration in the cement-water suspension through the reciprocal value: the "water-cement ratio") without including the amount and quality of the sand and stone in the models .

In concrete where the strength of the sand and stone is no longer high in relation to the strength of the binder, both the strength of the binder and the strength of the sand and stone will be of importance to the strength of the composite material.

This is known for traditional lightweight aggregate concrete where the stone material consists of light, porous , relatively weak material. In this case, the inherent strength of the stone has equal impor¬ tance to the strength of the mortar in the mathematical expression for the strength of the concrete:

σ = σ ⁿ a x σ m ^1"n

wherein σ is the compressive strength of the concrete, σ 3. is the compressive strength of the stone, σ is the compression strength of the mortar, n is the volume concentration of the stone, and 1-n is the volume concentration the mortar. In such materials , the rupture proceeds, to a large extent, through the weak stone particles .

With the development the new, very strong cement-based DSP binders , as disclosed in International Patent Application No.

PCT/DK79/00047, concrete and mortar with a hitherto unknown strength have been obtained. Thus, International Patent Applicatio No . PCT/DK79/00047 discloses water-cured, wet cylindrical test specimens having a diameter og 10 cm and a height of 20 cm and showing a compressive strength of 146.2 Mpa for a concrete after

169 days' storing at 20°C and 179 MPa for a mortar cured at about 60°C for 4 days . Both the concrete and the mortar were prepared from easily flowable masses cast with slight mechanical vibration. Traditional quartz sand and, for the concrete, granite stone, were used. These strengths were compared with the highest strength disclosed in the relevant technical literature:

120.6 MPa measured on test cylinders of the same dimensions as above and consisting of concrete with a water/cement ratio of 0.25, a cement content of 512 kg/m , and a content of "Mighty" (a concrete superplasticizer which is further characterized below) 150 in an amount of 2.75% of a 0.42% solution, calculated on the weight amount of cement, the samples having been stored for one year prior to the testing of compressive strength. (Kenichi Hattori, "Superplasticizers in Concrete, Vol. I, Proceedings of an inter¬ national Symposium held in Ottawa, Canada, 29-31 May, 1978, edited by V.M. Malhhotra, E .E . Berry and T. A. Wheat, sponsored by Canada Centre for Mineral and Energy Technology, Department of Energy, Mines and Resources , Ottawa, Canada and American Concrete Institute, Detroit, U. S .A. ) .

The investigation of rupture surfaces in connection with the strength measurements disclosed in International Patent Application No . PCT/DK79/00047 indicated that the sand and stone materials used were not strong in comparison with the binder such as would have been the case in normal concrete, as the rupture proceeded, to a large extent, through the sand and stone particles .

This indicated the possibility of producing even stronger concrete by combining the use of the DSP binder with the use of much stronger sand and stone materials . This is a principle which does not have any significant effect in connection with normal concrete,

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such as explained above .

The combination of the DSP binder with very strong sand and stone materials is one of the main aspects of the present invention.

In accordance with this aspect, concrete and mortar were prepared with the DSP binder, using, as sand and stone material, e.g. , refractory grade bauxite and silicon carbide, both of which are much stronger than ordinary concrete sand and stone, vide Examples 1 and 4.

The concrete and the mortar were prepared from easily flowable masses and had extremely high strength (the compressive strength of the cylindrical concrete specimens with diameter 10 cm and height 20 cm cured at 60°C for 4 days was 217 Mpa) .

This is more than 50% higher than the strength of the very strong concrete with traditional sand and stone, bound together with the new strong cement binder (146.2 MPa, cf . International Patent Application No . PCT/DK79/00047) and more than 80% higher than the highest strength which has, to the applicants' best knowledge, been obtained with concrete fabricated with traditional soft mass casting and curing technique using traditional superplasticized cement binder (120.6 Mpa, cf . Hattori, loc . cit) .

The new high quality material of the invention also showed an extremely high rigidity (dynamic modulus of elasticity of 109 ,000 MPa) which is about 60% higher than for high quality concrete using the DSP binder and quartz sand and granite stone, cf . Example 1 of International Patent Application No . PCT/DK79/00047.

The mortar with sand of refractory grade bauxite wass even stronger and more rigid than the concrete (the compressive strength of cylindrical specimens with diameter 10 cm and height 20 cm cured at 80°C for 4 days was 248 MPa and the dynamic modulus of elasticity was as high as 119,000 MPa, cf . Example 4) . The compressive strength is 38% higher than the strength of the

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strongest mortar prepared with the DSP binder and quartz sand (179 MPa, vide Example 9 of International Patent Application No . PCT/DK79/00047 and more than twice as high as the strength of the above-mentioned strong concrete reported by Hattori (120 MPa) . Still stronger cement-based DSP materials of the present invention have been made with the strong sand and stone materials vide Example 5 where the strength was 268.3 MPa.

Hence, the DSP concrete material of the present invention is of a hitherto unknown quality obtained by using extremely strong sand and stone material together with the extremely strong DSP binder, whereby

1) the strength of the sand and stone materials compared to ordinary concrete is utilized better, and

2) the strength of the DSP binder is utilized much better than in concrete with usual sand and stone material.

Together with the advantages with respect to easy production which are associated with the DSP binder, the incorporation of the particularly strong sand and stone materials opens up the possibilit of a wide range of new and improved products .

Another very interesting aspect of the ultra strong cement-based

DSP materials is the ratio between the strength σ and the density p which is the key parameter in the construction of large structures such as towers , bridges , etc . , where the maximum possible size is proportional to this ratio . The stress/density ratio of cement-based DSP materials and, in particular, of DSP materials comprising strong sand and stone, is far higher than that of ordinary concret or high quality concrete and even higher than the stress/density ratio of structural steel, cf . the ^" values stated in the following section "LARGE STRUCTURES" .

The aspect of the invention comprising ultra strong cement-based DSP materials may be defined as shaped articles comprising a

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coherent matrix,

the matrix comprising

A) homogeneously arranged inorganic solid particles of a size of from about 50 A to about 0.5 μm, or a coherent structure formed from such homogeneously arranged particles , and -

B) densely packed solid particles having a size of the order of 0.5 - lOOμm and being at least one order of magnitude larger than the respective particles stated under A) , or a coherent structure formed from such densely packed particles ,

the particles A) or the coherent structure formed therefrom being homogeneously distributed in the void volume between the particles B) ,

the dense packing being substantially a packing corresponding to the one obtainable by gentle mechanical influence on a system of geometrically equally shaped large particles in which locking surface forces do not have any significant effect,

the shaped article additionally comprising, embedded in the matrix,

C) compact-shaped solid particles of a material having a strength exceeding that of ordinary sand and stone used for ordinary concrete, typically a strength corresponding to at least one of the following criteria:

1) a die pressure of above 30 MPa at a degree of packing of 0.70, above 50 MPa at a degree of packing of 0.75, and above 90 MPa at a degree of packing of 0.80, as - - assessed (on particles of the material having a size ratio between the largest and smallest particle substantially not exceeding 4) by the method described herein,

2) a compressive strength of a composite material with

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the particles embedded in a specified matrix exceeding 170 MPa (in case of a substantial amount of the particles being larger than 4 mm) and 200 MPa (in case of sub¬ stantially all particles being smaller than 4 mm) , as assessed by the method described herein,

3) a Moh's hardness (referring to the mineral consti¬ tuting the particles) exceeding 7 and

4) a Knoop indentor hardness (referring to the mineral constituting the particles) exceeding 800,

. said particles having a size of 100 μ - 0.1 m,

and optionally

D) additional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A)

with certain provisos which will be explained below.

According to the above-mentioned aspect of the present invention, sand and stone materials are used which are stronger than the sand and stone materials used in ordinary concrete . Typically, concrete sand and stone consist of ordinary rock such as granite, gneiss , sandstone, flint and limestone comprising minerals such as quartz, felspar, mica, calcium carbonate, silicic acid etc.

* Various kinds of comparison tests may be used to assess that particular sand and stone materials are stronger than ordinary concrete sand and stone, e . g.

' 1) measurement of hardness 2) determination of the crushing strength of a single particle 3) hardness of the minerals of which the sand and stone materials are composed 4) determination of resistance to powder compression

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5) abrasion tests

6) grinding tests

7) measurement of strength on a composite material containing the particles .

It is difficult to specify unambiguous relations between such strength and hardness results for the sand and stone and the ability of the sand and stone to impart strength to the concrete or the mortar.

Generally, it must be anticipated that sand and stone with higher hardness , abrasion strength, strength in composite structure etc . , yields a higher concrete strength provided

1) identical particle geometry (particle shape, particle size, amount and degree of packing) and

2) the concrete systems are systems where, to a certain degree, rupture passes through the sand and stone particles . (In case the last condition is not fulfilled it is , as mentioned in the introduction of this specification, due to the fact that the sand and stone material in any case is far stronger than the matrix and that additional increase of the strength of the sand and stone has no influence on the rupture, the rupture then in any case passing through the matrix, avoiding the sand and stone particles . )

In Examples 1, 3, 4, and 5, sand and stone materials with con¬ siderably higher strength and hardness than ordinary concrete have been used:

Refractory grade bauxite containing 85% A O _o (corundum) and silicon carbide were used. Both materials have considerably higher hardness than the minerals in ordinary sand and stone . Thus , both corundum and silicon carbide are reported to have a hardness of 9 according to Moh's hardness scale, and the a Knoop indentor hardness is reported to be 1635 - 1680 for aluminum oxide (corun-

dum) and 2130 - 2140 for silicon carbide, while quartz, which is one of the hardest minerals in ordinary concrete sand and stonel, has a Moh's hardness of 7 and Knoop indentor hardness of 710 - 790 (George S . Brady and Henry R . Clauser, Materials Handbook, 11th ed. , McGraw - Hill Book Company) .

The high strength of these materials compared to ordinary concrete sand and stone has been demonstrated by powder compaction tests (Example 3) and by tests with mortar and concrete with silica-ceme binder where the materials were used as sand and stone (Examples

1,4, and 5) .

Many other materials than the two above-mentioned materials may, of course, be used as strong sand and stone materials . Typically, materials with a Moh's hardness exceeding 7 may be used, e.g. topaz, lawsonite, diamond, corundum, phenacite, spinel, beryl, chrysoberyl, tourmoline, granite, andalusite, staurolite, zircone, boron carbide, and tungsten carbide .

The hardness criterion could, of course, also be stated as Knoop indentor hardness where minerals having values above the value of quartz (710 - 790) must be considered strong materials compared with the minerals constituting ordinary concrete sand and stone . For the assessment of the strength of sand and stone, the tech- nique described in Examples 1, 4, and 5 involving embedding the sand and stone in question in a specificed cement/silica matrix produced and tested in a specified manner may be used:

Concrete (size of the larget particles exceeding 4 mm) :

Concrete produced from ordinary concrete sand and stone (granite stone and quartz sand) and silica/cement matrix substantially identical with the one used in Example 1 had compressive strengths about 120 - 160 MPa (vide International Patent Application No . PCT/DK79/00047) . Therefore, it seems reasonable to characterize stone and sand increasing the compressive strength of the concrete to 170 MPa as strong

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compared to ordinary concrete sand and stone. With refractory grade bauxite sand and stone, however, cf . Example 1 of the present application, strengths of 217.5 MPa were obtained, for which reason values above 200 MPa can be taken as a realistic and desirable goal for a preferred material.

Mortar (particle size not exceeding 4 mm) :

Analogous experience has been obtained with cement/silica mortar where materials with substantially identical cement/ silica matrix yielded compressive strengths of 160 - 179 MPa for quartz sand mortar (vide Example 9 in International Patent Application No . PCT/DK79/00047) and 248 and 268 MPa, respectively, for mortar with sand of refractory grade bauxite (Examples 4 and 5, respectively, of the present application) . It would seem reasonable to characterize sand which increases the mortar strength to above 200 MPa as strong compared to the strength of normal sand, and also, it seems reasonable to state strengths above 220 MPa as a goal which is both desirable and obtainable with the preferred materials .

For the evaluation of aggregates having a particle size exceeding 4 mm, the concrete technique from Example 1 is used. For the evaluation of sand having a particle size of less than 4 mm, the mortar technique, cf . Example 9 in International Patent Application No . PCT/DK79/00047 and Examples 4 and 5 in the present appli¬ cation (composite as for bauxite mortar) is used, whereby, in the particular mixes , the same volume of sand an stone is to be incor- porated, not the same weight amount of sand and stone . The pre¬ paration, the curing, and the testing are performed as in the examples mentioned.

The above-mentioned testing methods , and the particular way in which certain of the tests are performed, form the basis of the definition of useful and preferred particles C referred to in the claims .

The additional bodies D having at least one dimension which is at least one order of magnitude larger than the particles A may, in principle, be bodies of a solid (such as discussed in greater detail below) , a gas (such as in gas concrete) , or a hquid. The bodies may be compact shaped bodies (such as sand, stone, gas bubbles , or liquid bubbles) , plate-shaped (such as mica) , or elongated (such as fibers or reinforcing bars or wires) . Due to the possi¬ bility of shaping the articles in question in a "gentle" way in a low stress field, such bodies may, in contrast to what happens in any known art compaction processes which might achieve dense packing in ultra fine particle systems , substantially retain their geometric identity during the shaping. In this context, retainment of geometric identity indicates that the bodies in question ar not subjected to any substantial crushing or drastic deformation . A typical example is a solid body in the form of a hollow particle or a fiber which in powder compaction or other high stress field treatment would be crushed or drastically deformed, but which in the much lower stress field in which the articles of the invention may be formed is capable of avoiding such deterioration .

Examples of additional bodies D which are advantageously incor¬ porated in shaped articles comprising the DSP matrix, in particular the cement-based DSP matrix, are sand, stone, polystyrene bodies , including polystyrene spheres , expanded clay, hollo glass bodies , including hollow glass spheres , expanded shale, perlite, natural lightweight aggregate, gas bubbles , metal bars, including steel bars , fibers, including metal fibers such as steel fibers , plastic fibers, glass fibers , Kevlar fibers , asbestos fibers, cellulose fibers, mineral fibers, high temperature fibers and whiskers , including inorganic nonmetallic whiskers such as graphite whiskers and A D whiskers and metallic whiskers such as iron whiskers , heavy weight components such as particles of baryte or lead or lead; containing mineral, and hydrogen-rich components such as hollow water-filled particles . When the shaped articles comprise additional bodies D , it may be attractive for optimum strength and rigidity or for other purposes to obtain dense packing of the additional bodies . The easily deformable (easily flowable) DSP

02.IPI

matrix permits a considerably denser arrangement of additional bodies than was obtainable in the known art.

Especially the incorporation of fibers is of great interest due to the unique capability of the DSP matrix with respect to anchoring fibers . In this context, it should be mentioned that the much denser structure in the shaped articles comprising the DSP matrix will result in a virtual insulation of fibers otherwise subjected to chemical attack from the constituents of the matrix or from the surroundings . The fibers used in the shaped articles may be of anj ⁷ configuration such as chopped single fibers , or continous fibers or yarns or ropes , or roving or staple fibers , or fiber nets or webs . The particular type and configuration of fiber will depend upon the particular field of use, the general principle being that the larger the dimensions of the shaped article, the longer and coarser are the fibers preferred.

The improvement of the fixation of fine fibers makes it possible to fabricate strongly improved fiber composite materials based on mixing, into the material, a larger amount of chopped fibers than in corresponding materials based on common matrices . To secure a good fiber performance in the known art matrices, it is necessary that the chopped fibers have a certain (high) length to diameter ratio, the so-called aspect ratio. In normal matrices it is , how- ever, difficult to intermix and arrange fibers with large aspect ratios - in other words , the smaller the aspect ratio is, the easier it is to incorporate the fibers and arrange them in a suitable way in the cast matrix, and the higher volume of fibers can be incor¬ porated. For example, chopped polypropylene fibers with cross dimensions of approximately 30 μ, usually have a length of 12 -

25 mm (aspect ratio more than 500) when employed as reinforce¬ ment in ordinary cement matrices . A far better utilization of the same type of fibers is obtained in the DSP matrix, such as de¬ scribed in Example 2 of International Patent Application No . PCT/DK79/00047. In Example 2 of International Patent Application

No. PCT/DK79/ 00047, very favourable fixation and resulting strength properties were obtained even though the fiber length

was only 6 mm . With the DSP matrix, it seems possible to reduce the length of chopped fibers and, hence, the aspect ratio , with a factor of 10 or more (compared to chopped fibers of ideal or reasonable aspect ratios for use in normal matrices) and, accor- dingly, to utilize this reduced aspect ratio to incorporate a larger amount of fibers in the composite material and/or secure a better fiber arrangement in the cast matrix.

The above-mentioned polypropylene fibers used in Example 2 of International Patent Application No . PCT/DK79/00047 can be characterized as polypropylene fibers having a tensile strength of

2 at least 4000 kp/cm , a modulus of elasticity of at least

7 x 10 4 kg/cm 2 , and an elongation at rupture of at the most 8%.

Such fibers may be prepared by stretching a polypropylene film in a ratio of at least 1: 15 to obtain a film thickness of 10 - 60 μ and fibriHating the stretched material by means of a rotating needle or cutter roller to obtain fiber filaments of from about 2 to about 35 dtex. This technique is disclosed in German Patent Application No .

P 28 19 794.6, and US patent No. 4, 261,754.

Among the most important shaped articles comprising the DSP matrix are the ones in which the particles B comprise at least 50% by weight of Portland cement particles , especially the ones in which the particles B essentially consist of Portland cement par- tides . These shaped articles will typically contain silica dust particles in a volume which is about 5 - 50% by volume, in particular 10 - 30% by volume, of the total volume of the particles A and B and will typically contain sand and stone as additional bodies to form mortar or concrete of extremely high qualities with respect to mechanical strength, frost resistance, etc . , and/or fibers , especially metal fibers , including steel fibers , mineral fibers , glass fibers , asbestos fibers , high temperature fibers, carbon fibers, and organic fibers , including plastic fibers , to provide fiber- reinforced products showing a unique anchoring of the fibers such as discussed further above . With particular reference to fibers which are subject to chemical deterioration , for example glass fibers which are subject to deterioration under

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highly alkaline conditions , it is an important advantage of the DSP matrix that such fibers , both during the curing of the material and in the final cured material, become much better protected against influence from the environment, due to partial dissolution of the silica dust with resulting partial neutralization of the alkaline environment, and due to the micro- dense "jacketing" around the fibers conferred by the ultra fine particles and the coherent structure formed therefrom which very substantially contributes to static conditions in the glass fiber environment, substantially avoiding any migration of alkaline material against the fiber in the final cured matrix.

When the shaped articles comprising the cement-based DSP matrix are of large sizes , they are preferably reinforced with reinforcing steel such as bars or rods or steel wires or fibers . Reinforcements in pre-stressed constructions involving the DSP matrix are es¬ pecially valuable . Due to the very gentle conditions under which the articles can be shaped, the reinforcement bodies can retain their geometric identity during the shaping process . A combination showing the matrix structure discussed above and reinforcing steel that had retained its geometric identity during the shaping process was hardly obtainable in the known art systems .

With the considerably increased strength of the DSP matrix and the strongly improved fixation of fibers and bars in the matrix, possibilities for producing new classes of reinforced and fiber- reinforced cement based articles and materials are provided:

1) Brittle materials with very high tensile strengths obtained by incorporating high quality fine fibers or whiskers (fibers or whiskers of high tensile strength and high modulus of elasticity, for example glass fibers , carbon fibers , asbestos , - - A _j Oo whiskers) in a medium to high volume concentration into the binder matrix.

2) Semi-brittle materials with high tensile strengths and comparatively large strain capacity obtained by incorporating

high quality relatively fine fibers with high tensile strength and relatively low modulus of elasticity in a medium to high volume concentration into the binder matrix (for example, high strength polypropylene fibers and Kevlar fibers) .

3) High performance pre-stressed reinforced articles , the quality being primarily obtained by incorporating a much higher volume of high quality steel bars or wires than ordi¬ narily used (the volume of reinforcement that can be utilized being directly proportional to the compressive strength of the matrix) in a matrix of the new type according to the- invention In ordinary pre-stressed concrete, the volume of pre-stressin steel is as low as 1 - 2% of the concrete.

The volume of the steel is limited by the compressive strength of the concrete. An increase of the compressive strength with a factor of 4 could, for example, be fully utilized in pre- stressing members to secure a 4 times higher bending capa¬ city or to decrease the height of the member to one half . Such members would demand a not unrealistic high volume of pre-stressing steel (4 - 8%) . It would also be possible to apply the improved matrix material in pre-stressed articles of much smaller cross section than in traditional pre-stressed concretes , with a corresponding use of finer pre-stressing reinforcement (thin wires) . In spite of the larger specific surface, the wires are well-protected in the dense DSP matrix material which effectively shields the wires from any influence from the surroundings .

4) Articles of reinforced, not pre-stressed concrete where the improved quality of the matrix material is primaril}' utilized by incorporating steel bars or wires of a much higher tensile _ strength than in the ordinary steel reinforced concrete . The use of an increased amount of an ordinary reinforcement to benefit from the increased qualtfy of the matrix would in many cases demand an unrealistically high amount of rein¬ forcement. High quality reinforcement bars used in ordinary

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concrete has a surface which is shaped so as to secure their anchorage in the concrete (deformed bars ; cam steel; tentor steel; etc . ) . Such bars have a strength not exceeding 900 MPa and, hence, do not have the same high strength as the best cold drawn smooth bars and wires used for example in pre-stressed concrete which typically have strength of 1800 - 2200 MPa. On the other hand, smooth wires and bars do not secure sufficient fixation in ordinary concrete. The strongly improved fixation obtained in the DSP matrix opens up the possibility of a beneficial utilization of the very high strength smooth steel wires and bars as non-prestressed reinforcement. Due to large strain when fully utilizing the high steel quality and the corresponding cracks which will occur in the concrete (as in usual reinforced concrete) it is advisable especially to use the above-mentioned technique in thin members in combi¬ nation with fine reinforcement in order to secure a crack pattern with several finer distributed thin cracks .

The reinforcing possibilities mentioned may, of course, be combined in many ways, for example by making a thin cover of semi-brittle reinforced material on a large load bearing member, or by use of high quality steel wires as secondary reinforcement (mainly placed perpendicular to the main reinforcement) in large pre-stressed members .

When strong sand and stone (bodies C) are embedded in the matrix in accordance with the above- described aspect of the present invention, the resulting high quahty DSP materials may be characterized in that they have a compressive strength of

more than 150 MPa, preferably more than 180 MPa, measured on a test specimen having a diameter of 10 cm and a height - - of 20 cm, when the largest of the compact- shaped bodies is larger than 4mm, and

more than 180 MPa, measured on a test specimen having a diameter of 3 cm and a height of 6 cm, when the largest of

the compact- shaped bodies is at most 4 mm .

with the proviso that the shaped article has at least one dimension

2 which is at least one meter and a cross section of at least 0.1 m , and/or has a complex shape which does not permit its estabhshmen by powder compaction .

PROPERTIES OF FLUID STRUCTURE; WATER RETENTION .

By introducing ultra fine particles in the voids between densely packed particles , for example silica particles having a specific

2 surface area of 250, 000 cm /g in the voids between cement particles having a diameter about 5 μm, a structure is obtained which shows an increased resistance against internal mass transport in the form of fluid transport (gas or hquid) between the particles and against mass diffusion in the pore hquid.

The squeezing of Hquid from saturated particle systems depends on the compression of the particle skeleton - typically depending on whether sliding between the particles is possible - and on the flow of Hquid through the channels between the particles .

In connection with shaping of cement-sϋica- water suspensions , internal Hquid transport in the fresh material is of decisive importance . The resistance against viscous flow of fluid between particles in systems of particles of geometrical similarity varies inversely as the square of the particle diameter.

This means that the time for a given Hquid transport under a given pressure gradient in two geometricaHy similar particle-Hquid systems with a particle size of 1 : 50 is 2500 times higher in the fine grained system than in a system with particles are 50 times as large .

A similar effect is obtained by filling the pore volume between large particles with ultra fine particles , as it is the cross-section

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dimensions of the resulting channels between the particles which are mainly responsible for the resistance to the flow.

The effect of particle size on water retention is further illustrated in Figs . 6, 7, and 8. These facts are weH-known, and it is also known art to reduce the internal Hquid transport in cement/water systems by introducing so-caHed "thickeners" in the water in the form of ultra fine particles or polymers such as MethoceH.

Because of the dominating effect of locking surface forces , it wiH, however, normaHy not be possible to combine the uses of 1) very dense cement packing and 2) ultra fine particles in an easily flowable aqueous suspension.

However, with an extremely high dosage of a dispersing agent, such as a superplasticizer, this is possible. Thus , easily flowable cement paste, mortar and concrete with densely packed cement particles and containing 10 - 30 per cent by volume of silica dust, calculated on cement + siHca dust, with water/cement + siHca-ratio of 0.15 - 0.20 by weight can be made.

This results in several advantages compared to the known methods :

1. Production of superfluidized cement product without bleeding.

In the known art production of high quaHty concrete and mortar using relatively high dosages of superplasticizer, an easHy flow¬ able mass having a low water/ cement-ratio (for exampel 0.25) is obtained. The mass is poured into moulds where it is compacted under the influence of gravity and optionaHy also mechanical vibration . However, during this process , the heavier cement, sand, and stone particles wiH tend to arrange themselves in an even more dense packing, while water migrates upwardly, the so-caHed bleeding, vide Fig. 7.

Accordingly, for such known systems with very efficient cement dispersion obtained in the use of relatively high dosages of super-

plasticizer, a marked bleeding is normaHy observed in spite of the low water/cement-ratio - especiaHy if the process is accompanied by vibration. This phenomenon may for example be critical in the casting of concrete roads with superplasticized concrete as bleeding results in a surface sludge of high water content, and hence re¬ sults in a road surface which has a lower quahty than the intended abrasion layer. Internal Hquid separation is also critical in casting of reinforced concrete with superplasticizer. The Hquid separation may result in a bleeding at the underside of the reinforcement, which reduces the fixation of the reinforcement and reduces the protection against chemical attacks .

By introducing, in accordance with the principles of the present invention, ultra fine particles, for example 5 - 15% of siHca dust having the above-mentioned particle size, between the densely packed cement particles, and using a high dosage of superplasti¬ cizer, a drastic delay of the bleeding process is obtained, theore- ticaHy corresponding to 100 - 1000 times slower water movement (vide Fig. 8) . In practice, this means that bleeding has been obviated, considering that the chemical structuring process nor¬ maHy starts and develops much faster.

In other words , utilizing the above-mentioned principle of the invention of combining high dosage of superplasticizer with siHca dust, it becomes possible in practice to produce superfluidized high quahty contrete, mortar and cement paste without bleeding. This is of special interest in connection with pre-stressed con¬ structions , where the above-mentioned principles can be utilized for producing high quaHty non-bleeding, easHy flowing injection mortar (grouting mortar) which gives extremely good protection of the tendons and secures an extremely good mechanical fixation , vide the more detailed discussion of this aspect below.

2. Production of high quaHty cement products in a low stress field and without Hquid transport to the surroundings .

In the production of certain cement products , for example asbestos

- ORE

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cement panels , the known art technique presently used is either a shp-casting technique (in which surplus Hquid is pressed out from a aqueous slurry through filters , cf . the Magnani process in which the pressing is estabhshed via a vacuum system) or a high pres- sure extrusion of a moist powder (where a traditional thickener

(MethoceU) has been added to obviate the otherwise hardly avoid¬ able internal Hquid transport at the outlet and the consequent blocking of the system by particle interlocking) .

According to one aspect of the invention, it becomes possible to produce such materials in a low stress field by simple rolling pro¬ cesses or extrusion without Hquid exchange with the surrounding when a high amount of superplasticizer is incorporated in the mass together with ultra fine particles .

While it might seem possible to employ similar rolling or extrusion processes with cement materials with high amount of superplasti¬ cizer incorporated, but without the concomitant use of ultra fine particles which is characteristic to this aspect of the present inven- tion, such materials - although they could be made easily flowable with a low water/powder- ratio (but not quite as low as with ultra fine, weH dispersed particles) - would, due to the large size of the cement particles , show a marked tendency to local water ex¬ pulsion in the stressed zones , such as at the roHers or at the outlet in extrusion, with resulting blocking of the particles . This has been observed in practice in experiments with a laboratory extruder with superplasticized, fine grained cement and with superplasticized ordinary cement plus an additive of a fine fiHer which was finer than the cement, but considerably coarser than the above-mentioned ultra fine siHca dust. In both cases , the material had a sandy performance and could not be extruded due to blocking.

With an ultra fine siHca powder incorporated in the superplasti- cized cement system in accordance with the principles of the present invention, such expulsion of water is delayed with a factor of the order of 100 - 1000 (as calculated from theoretical considerations) .

The appearance of the cement siHca material containing a high amount of superplasticizer is toughly-viscous and cohesive during rolling, while corresponding superplasticized products without the ultra fine siHca powder typicaHy appear as friction materials with a tendency to local water expulsion with resulting particle blocking during rolling or extrusion .

3. Production of easily flowable materials with a high internal coherence .

Easily flowable superplasticized cement materials containing ultra fine siHca particles are one aspect of the DSP principle and show a much better internal coherence than corresponding superplasticized easHy flowable cement materials without ultra fine siHca particles . This, is beHeved to be due to the fact that local Hquid transport which contributes to separation, is drasticaHy reduced in the materials with the ultra fine siHca particles .

(This is iHustrated in Fig. 10, which iHustrates a demonstration of internal coherence of a fluid to plastic mortar. The influence of streaming water (4 Hters per minute) for typicaHy 5 to 30 minutes wiH not result in any visible washing away of material from the mortar . )

Many advantages are obtained in this manner. For example, the existing possibilities of producing underwater concrete by simple pouring the fresh concrete into the water are considerably improve

Such a technique is known per se and especiaHy developed with superplasticizing additives (without ultra fine powder) . However, with ultra fine, weH-dispersed siHca powder in accordance with the principles of this invention, the process is now much more attrac¬ tive -and shows correspondingly extended potential fields of utiHty .

The resistance against internal Hquid transport increases with the density of the packing of the ultra fine particles in the voids between the coarse particles . Thus , it is expected that fluidized

OM

powder materials consisting of weU-dispersed Portland cement (s =

4000 cm 2 /g) and siHca dust (s = 250,000 cm 2 /g) wiH show con¬ siderably better internal coherence, higher resistance to internal Hquid flow and bleeding, and better processabiHty in rolling and extrusion with 20 - 40 volume per cent of siHca dust than at 5 -

10 per cent. However, the experience so far obtained indicates that even very smaH amounts of ultra fine siHca dust (typicaHy 1 - 5%) incorporated between densely packed particles b) , in par¬ ticular in densely packed Portland cement structures may have a marked improving effect compared to similar materials without siHca dust.

Other important aspects of the invention are duct and fissure fil¬ lings of cured grout.

Grout normaHy consists of cement and water, usuaUy with admix¬ tures to improve performance. The two main objectives in grouting ducts in post tensioned concrete members are to prevent corrosion of the tendons and to provide bond between the pre-tensioned steel and the concrete. The most important properties of the grout to be pumped in the ducts are fluidity and water retention (low bleeding) .

Fluidity is essentially a function of the water/cement ratio . Re- ducing the water content produces a stiff er less fluid mix, the effect being more marked at lower water/cement ratios . In general, the water/cement ratio of good grout Hes between 0.35 and 0.50.

There are a number of additives such as dispersing agents which improve the fluidity for a given water/cement ratio, or alternatively , reduce the water/cement ratio required to obtain a given fluidity, but their effect on other properties of the grout, especiaHy the bleeding, often limits their use.

Before grout sets , water can segregrate from the mix due to the sohd particles being heavier than the water - often termed "blee¬ ding" . This may inter aha result in highly undesirable water pockets at the underside of the pre-stressed steel. Bleeding is

^\j RE_A

increased with increased water/cement ratio and with increased amount of dispersing agent (for example, a fluid cement paste having a water/cement ratio as low as 0.25, obtained with a high dosage of concrete superplasticizer, shows, in spite of the very low water/cement ratio, marked bleeding) . Anti-bleed-additives are available which produce a thixotropic mix exhibiting virtuaHy no bleeding. None of them, however, have hitherto been compatible ^■ with a combination of high fluidity and very low water/cement ratio. Furthermore, most of these additives are based on a ceUulose ether which reduces the strength and retards the setting time. With grout according to the present invention, (for example a cement-siHca-Mighty-grout having a water/ cement plus siHca dust ratio of 0.15 - 0.18) , the foHowing is obtained:

l) A much denser and stronger grout than hitherto having strongly improved fixation of the pre-stressing steel (probably corresponding to a factor of 4 - 10, cf . Example 10 of Inter¬ national Patent AppHcation No . PCT/DK79/00047 ) and protection of the steel against corrosion,

2) the said grout being, in spite of the extremely low water/powde ratio, easHy flowable and suitable for being pumped into and fiH out the ducts with virtuaHy no bleeding, the additives (ultra fine inorganic particles such as siHca dust and a concrete superplasti- cizer) having no adverse effect on the setting of the grout, on the contrary,

3) resulting in a very high early strength.

NormaHy, grout for injection in ducts in connection with post- stressed concrete does not contain coarser particles (sand) , as this would impede the flow of the mass . Grout according to the invention may, like conventional grout, be without any content of sand or any other additional bodies . However, the strongly improved coherence of the fluid mass of the invention with virtuaHy no bleeding makes it possible to introduce sand into the grout therebj'' obtaining an even more rigid hardened structure, at

O . W WII

the same time retaining an easHy flowable grout. This has been demonstrated in an experiment (Example 11 in International Patent AppHcation No . PCT/DK79/00047) where fluid coherent cement-sihca mortar containing sand up to 4 mm was easHy poured into an about 2.5 m long very narrow duct (18 mm diameter) , mainly due to the action of gravity, thereby forming a very dense structure .

Along the very same line, the invention also makes it possible to produce strongly improved prepacked concrete (where voids between the pre-placed stones are fiHed with a fluid mortar) . The improvement obtained through the non-bleeding highly fluid mortar obtained according to the present invention may be utilized both in dry-casting and in sub-water-casting.

A special way of injecting grout, securing both good filling of narrow spaces (typicaHy with paste) and filling of large bulk cavities with coarser particles (typicaHy with concrete) by a two-step method is dealt with in the section ""MULTI-STAGE INJECTION" .

MANUFACTURING METHODS .

Articles comprising the DSP matrix may be shaped in a low stress field from a composite material comprising

A) bodies of a size of from about 50 A to about 0.5 μ ,

B) bodies having a size of the order of 0.5 - 100 μ , and being at least one order of magnitude larger than the re¬ spective particles stated under A) ,

opjtiqnaHy

C) compact-shaped sohd particles of a material having a strength exceeding that of ordinary sand and stone used for ordinary concrete, typicaHy a strength corresponding to at

least one of the foHowing criteria:

1) a die pressure of above 30 MPa at a degree of packin of 0.70, above 50 MPa at a degree of packing of 0.75 , and above 90 MPa at a degree of packing of 0.80, as assessed (on particles of the material having a size ratio between the largest and smaHest particle substantially not exceeding 4) by the method described herein,

2) a compressive strength of a composite material with the particles embedded in a specified matrix exceeding 170 MPa (in case of a substantial amount of the particles being larger than 4 mm) and 200 MPa (in case of sub¬ stantiaHy aH particles being smaHer than 4 mm) , as assessed by the method described herein,

3) a Moh's hardness (referring to the mineral consti¬ tuting the particles) exceeding 7 and

4) a Knoop indentor hardness (referring to the mineral constituting the particles) exceeding 800, said particles having a size of 100 μ - 0. 1 m,

a Hquid,

and a surface-active dispersing agent,

the amount of bodies B substantiaHy corresponding to dense packing thereof in the composite material with homogeneously packed bodies A in the voids between bodies B , the amount of

Hquid substantiaHy corresponding to the amount necessary to fiH out the voids between particles A and B , and the amount of dis¬ persing agent being sufficient to impart to the composite material a fluid to plastic consistency in a low stress field of less than 5 kg/cm , preferably less than 100 g/cm ,

and optionaHy

Q P WIP

D) additional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A) .

It is to be noted that although the amount of surface active dis- persing agent is defined in claim 30 by stating the conditions which must be fulfilled in order that the amount be sufficient to disperse the particles in a low stress field (which, expressed in another way, indicates the use of an extremely high amount of the surface activity dispersing agent) , this does not mean that the composite material is necessarily used in a low stress field; it may also be used in a higher stress field. Articles with densely packed superfine particles are obtained from a composite material of the above type where the particles A are present in a volume substan¬ tiaHy corresponding to dense packing to fiH the voids between the particles B when densely packed.

The surface- active dispersing agent is present in an amount suf¬ ficient to aHow dense packing of the particles A) in a low stress field of less than 5 kg/cm 2 , preferably less than 100 g/cm 2 , and the ideal amount of the dispersing agent is one which substantiaHy corresponds to the amount which wiH fuUy occupy the surface of the particles A . Fig. 2 in International Patent AppHcation No . PCT/DK79/00047 shows ultra fine siHca particles covered with a layer of a dispersing agent, a so-caHed superplasticizer "Mighty" , the composition of which is described below. Under the assumption that the superplasticizer is absorbed in a uniform layer at the surface of the siHca spheres , the calculated thickness, with refe¬ rence to appHcant's own experiments, was 25 - 41 Angstrom, corresponding to a volume of 14 - 23% of the volume of the spheres . It is to be noted that a surplus of the dispersing agent over the amount which wiH fuHy occupy the surface of the ultra fine particles , wiH not be advantageous and wiH only tend to take up too much space in the composite material.

Any type of dispersing agent, in particular concrete super- plasticiser, which in sufficient amount wiH disperse the system in a low stress field is useful for the purpose of the invention . The

concrete superplasticiser type which has been used in the experi¬ ments described in the Examples to obtain the extremely valuable results in Portland cement-based systems is of the type comprising alkaH and alkaline earth metal salts , in particular a sodium or calcium salt, of a highly condensed naphthalene sulphonic acid/for¬ maldehyde condensate, of which typicaHy more than 70% by weight consist of molecules containing 7 or more naphthalene nuclei. A commercial product of this type is caHed "Mighty" and is manu¬ factured by Kao Soap Company, Ltd. , Tokyo, Japan . In the Portland cement-based siHca dust-containing composite materials according to the invention, this type of concrete superplasticiser is used in the high amount of 1 - 4% by weight, in particular 2 - 4% by weight, calculated on the total weight of the Portland cement and the siHca dust.

Other types of concrete superplasticizers useful for the purpose of the present invention appear from Example 2 of the present apphcation .

Portland cement-based composite materials of the type defined above wiH often contain additional fine particles of suitable size and size distribution together with the Portland cement particles , such as fine sand, fly ash, and fine chalk, to obtain even more dense binary structures formed from the particles B in accordance with the principles discussed above .

Both with respect to its unique shaping and workability properties as discussed above and illustrated in greater detaH in the examples below, and with respect to its capability of gently fixing and, in the final shaped state, extremely effectively micro-locking or micro- jacketing any incorporated additional bodies , the composite material shows uniquely advantageous properties which have not previously been reported or indicated for any material, and hence, such novel and extremely useful composite materials constitute important aspects of the present invention .

Interesting novel composite materials of the invention are Portland

cement-based or not Portland cement-based materials containing, as additional bodies , bodies selected from the group consisting of polystyrene bodies , including polystyrene spheres , expanded clay, hoHow glass bodies , including hoUow glass spheres , expanded shale , perhte, natural Hghtweight aggregate, gas bubbles , fibers, including metal fibers such as steel fibers , plastic fibers , glass fibers , Kevlar fibers , asbestos fibers , ceHulose fibers, mineral fibers , high temperature fibers and whiskers , including inorganic nonmetalHc whiskers such as graphite whiskers and Al„O„ whiskers and metallic whiskers such as iron whiskers , heavy weight components such as baryte or lead or lead-containing mineral, and hydrogen-rich components such as hoHow water-fiHed particles . When the composite material is Portland cement-based, that is, contains at least 20% by weight of Portland cement particles as particles B , sand and/or stone as sole additional bodies wiH result in important novel mortar and concrete composite materials .

Important composite materials of the present invention are the materials in which the particles A are siHca dust particles having a

2 specific surface area of about 50,000 - 2 , 000,000 cm ^' /g, in parti-

2 cular about 250, 000 cm /g, and the particles B comprise at least

50% by weight of Portland cement. In these composite materials , the dispersing agent is preferably a concrete superplasticiser in a high amount resulting in the above- defined dispersing effect.

In accordance with the principles discussed above, the composite material for making the articles of the invention has a very low ratio between water and cement and any other particles B + siHca dust, this ratio being 0.12 to 0.30 by weight, preferably 0. 12 to 0.20 by weight, and the silica dust may be present in a volume which is about 0. 1 - 50% by volume, preferably 5 - 50% by volume, in particular 10 - 30% by volume, of the total volume of the par- tides A + B .

In accordance with a special aspect of the invention, the composite material is packed and shipped as a dry powder, the addition of the Hquid, tj icaHy water, being done on the job . In this case,

- J REXζr- _ OMPI

the dispersing agent is present in dry state in the composite material. This type of composite material of the invention offers the advantage that it can be accurately weighed out and mixed by the producer, the end user just adding the prescribed amount of Hquid and performing the remaining mixing in accordance with the prescription, e. g. , in the manner described in Example 11 in International Patent AppHcation No. PCT/DK79/00047.

The invention also relates to a process for producing a shaped article, said process comprising combining

A) bodies of a size of from about 50 A to about 0.5 μ, and

B) bodies having a size of the order of 0.5 - 100 μ and being at least one order of magnitude larger than the respective particles stated under A) ,

a Hquid,

and a surface-active dispersing agent,

the amount of bodies B substantiaHy corresponding to dense packing thereof in the composite material with homogeneously packed bodies A in the voids between particles B , the amount of Hquid substantiaHy corresponding to the amount necessary to fiH the voids between particles A and B , and the amount of dispersing agent being sufficient to impart to the composite material a fluid to

2 plastic consistency in a low stress field of less than 5 kg/cm ,

2 preferably less than 100 g/cm ,

optionaHy

^~ - C) compact-shaped soHd particles of a material having a strength exceeding that of ordinary sand and stone used for ordinary concrete, typicaHy a strength corresponding to at least one of the foHowing criteria:

OMPI

1) a die pressure of above 30 MPa at a degree of packing of 0.70, above 50 MPa at a degree of packing of 0.75, and above 90 MPa at a degree of packing of 0.80, as assessed (on particles of the material having a size ratio between the largest and smaHest particle substantiaHy not exceeding 4) by the method described herein,

2) a compressive strength of a composite material with the particles embedded in a specified matrix exceeding 170 MPa (in case of a substantial amount of the particles being larger than 4 mm) and 200 MPa (in case of sub¬ stantiaHy aH particles being smaHer than 4 mm) , as assessed by the method described herein,

3) a Moh's hardness (referring to the mineral consti¬ tuting the particles) exceeding 7 and

4) a Knoop indentor hardness (referring to the mineral constituting the particles) exceeding 800,

said particles having a size of 100 μ - 0.1 m ,

and optionaHy

D) additional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A,

by mechanicaUy mixing the particles A, the Hquid, and the surface active dispersing agent, optionaHy together with particles B , par- tides C and/or additional bodies D , until a viscous to plastic mass has been obtained,

and thereafter, if necessary or if desired, respectively, combining the resulting mass with particles and/or bodies of the type men- tioned above (B , C , D) by mechanical means to obtain the desired distribution of the components , and finaHy casting the resulting mass in the desired shape in a stress field, optionaHy with in-

corporation of particles C and/or additional bodies D during the casting.

It should be noted that the low stress field stated defines the amount of dispersing agent to be used and does not necessarily mean that the process is in fact carried out in a low stress field.

However, the fact that it can be performed in a low stress field constitutes one of the main advantages of the process, and pre-

2 ferred low stress fields (which are preferably below 5 kg/ cm and more preferably below 100 g/cm ) used for shaping the mass are :

^{' '} gravity forces acting on the mass , such as self -levelling out of a cast soft mass , or forces of inertia acting on the mass , such as in centrifugal casting, or contact forces, such as pressure compaction rolling or extrusion, or the simultaneous acting of two or more of the above forces , such as in combined vibration and pressure compaction . Also, osculating forces with a frequency between 0.1 *? and 10 Hz may be used to shape the mass, the oscillating forces being of the type described above, such as forces from mechanical or hydrauHc vibrator, or such osculating forces may be combined with non- os dilating forces such as in combined vibration and pressure compaction .

For most practical purposes, the Hquid used in the process is water, and the dispersing agent is often added together with the water so that an aqueous solution of the dispersing agent is added, but it is also within the scope of the present invention to incor¬ porate the water separately from a solution of the dispersing agent, the dispersing agent being combined with the water in the mixing process . It is characteristic that a mixture conforming with the above-stated definition wiH have a very "dry" appearance during the mixing stage until it converts into a viscous plastic mass , this "dryness" being due to the low fluid content.

The fabrication technique for producing the shaped articles accor¬ ding to the invention must naturaHy be speciaHy adapted to the specific type of composite material in question and the specific type of shaped article in question . There are, however, some

general trends :

1) The powders of the matrix (particles A and B) should prefer¬ ably be avaHable as weH dispersed as possible before intermixing. If the dispersion in dry condition is insufficient, e .g. if par¬ ticles A are aggregated, some sort of dispersing action, such as grinding, may be appHed.

2) The mixing must secure homogeneous mutual distribution of the sohd particles A and B . This may be obtained by dry mixing or by wet mixing where a premix of Hquid and either particles A or particles B is mixed with the respective remaining particle type . This mixing step may be performed with or without additional bodies .

3) Incorporation of the Hquid either to the dry-mixed powder (particles A + B) or to either particles A or particles B in case of pre-mixing of a wet slurry as mentioned under 2) may be per¬ formed either by adding the powder to the Hquid (preferably under strong mechanical stirring) or by adding Hquid to the powder mass

(preferably under strong mechanical kneading) . Which of these methods to be used wiH largely be a question of experience . However, it is presently beheved that in preparing a relatively easHy flowing mass from weH-dispersed powder, the most easy method is to perform the mixing by adding the weH-dispersed powder to the stirred Hquid, to avoid the Hquid meniscus between particles which would occur in the reverse process in which smaH amounts of Hquid were added to the powder . On the other hand, when poorly dispersed ultra fine powder is added to the stirred Hquid, the powder may not be sufficiently dispersed by stresses introduced during stirring, even with addition of dispersing agent. In this case, incorporation of the Hquid in the powder under high shear kneading is preferable as the kneading in combination with dispersing agents may achieve a considerable dispersing effect. In the Examples (which are mainly based on Portland cement + siHca dust) , the method of adding Hquid to the powder under knead¬ ing/mixing (with a rather modest shear stress of approximately

2 100 - 1000 g/cm ) was appHed. For the most fluid materials

( orta-" and concrete with water/(cement + siHca) ratio of 0.18 to

0.20 by weight) it is beHeved that the reverse technique might have been used equaHy weH. For the more stiff mixes (pastes for extrusion containing fibers and with a water/ (cement + siHca) ratio of 0.13 to 0.15 by weight) it is , however, beHeved that the reverse technique would not work at aH; in these cases valuable part of the mixing occurred in the extruder where a relatively

2 high kneading took place (in the range of 1 kg/cm ) ,

4. The dispersing agent is not necessarily introduced as a solution in the Hquid (it might be added as a powder to be dry mixed together with the particles A and B) . For some systems , it is preferable to wet the surface of the particles with part of the Hquid before adding the solution containing the dispersing agent, such as it is recommended in the known art with superplasticized Portland cement suspensions. This was also done in the cement- siHca experiments described in the Examples of International Patent AppHcation No . PCT/DK79/00047, except in Example 11 thereof . It is worthwhHe to note that the mixing time of the very dense wet mix may be drasticaUy prolonged compared with traditional mixing. This was in particular the case for the relatively stiff mixes (extruded paste with water/(cement + siHca dust) ratio of 0.13 to 0.15, cf . Example 2 of International Patent AppHcation No. PCT/DK79/00047) and for the medium stiff mixes (water/(cement + siHca dust) ratio of 0.15 to 0. 16, cf . Examples 3 and 9 of Inter¬ national Patent AppHcation No . PCT/DK79/00047 where a mixing time of approximately 15 and 5 minutes , respectively, was neces¬ sary for changing the consistencs ^7- from an almost dry appearance to that of a dough and a fluid a viscous mass , respectively . For the concrete with a water/(cement + siHca dust) ratio of 0.18, there was also a prolonged mixing time, but not as marked as for the yery low water/powder ratio systems . It is beHeved that the local transport of the molecules of the dispersing agent to and between the surfaces of the densely packed soHd particles is the time-consuming factor of the process (this transport being more difficult, the s aHer the ratio water/powder is) . The consistency

of the material is very sensitive to the amount of Hquid. Thus , very smaH amounts of additional Hquid may change the consistency from stiff dough-like to easHy flowable . In a superplasticized cement- siHca mixture, this change can be achieved by changing the water/(cement + siHca dust) ratio from 0.14 to 0.18.

Introduction of the dispersing agent as a dry powder to the dry mix before adding water seems to be an equaHy valuable way of producing the casting mass of the invention . This was demonstrated in Example 11 of International Patent AppHcation No . PCT/DK79/-

00047 where this procedure was used, resulting in a mortar with substantiaHy the same flowabihty and appearance as one made from almost the same components, but mixed as described above with addition of the dispersing agent as a solution to the pre-wetted mix (vide Example 9, Mix No . 1, of International Patent AppH¬ cation No. PCT/DK79/00047) .

For any specific system, there is a level at which the system is saturated with superplasticizer and over which there is no benefi- cial effect in adding further superplasticizer. This saturation point increases with decreasing water/ (cement + siHca dust) ratio . Above this level, the material is not sensitive to the amount of dispersing agent.

5. The incorporation of the bodies and optionaHy D may be per¬ formed at any operational stage such as during the dry mixing or after wet mixing etc . The preferred technique to be used in the specific cases depends on the character of the bodies C and D and is a question of experience. In the case of concrete and mortar it is important to secure a relatively dense packing of the added sand and stone in order to secure a relatively s aH void to be fiHed with the dense binder matrix of the invention . When incor¬ porating fine fibers , usual techniques such as shaking/mixing, paddle mixing, and kneading mixing may be apphed. With incor- poration of continuous fibers or filaments or pre-arranged fibers such as fiber nets or webs , according to known technique, a valuable fiber orientation or fiber arrangement is obtainable . Quite

generaHy, the same techniques may be used for incorporating additional bodies in the matrix of the invention as for known matrices , but due to the substantial absence of locking surface forces between the particles, it wiH generaHy be easier to obtain efficient incorporation .

6. The casting, including compaction, may be obtained in the low-stress fields mentioned above . The new type of material wiH be weH-suited for transportation by pumping due to the substantial absence of bleeding, and the viscous character of the mass . As the casting mass, however, consists of a particulate matter with virtuaHy no locking surface forces between the individual particles, vibration and especiaHy high frequency vibration may strongly assist the casting, as the mutual osculating displacement of adjacen particles wiH considerably faciHtate the flowing.

7. The soHdification of the material of the invention differs from soHdification of the corresponding articles based on less densely packed matrices in two respects :

Firstly, as the structure is more densely packed, the soHdification wiH be faster (early strength) . Secondly, the soHdification may be influenced by the rather large amount of dispersing agent which is necessary in order to obtain the specific structure. In the Portland cement- sihca-Mighty systems , high early strength was obtained, but a modest retardation of the curing was noted (4 - 8 hours) . In the actual Portland cement- sihca-Mighty systems , it was shown, such as could be predicted from the expected calcium siHcate hydrate structure to be formed, that extremely good quaHty could be obtained by curing at as weH approximately 20°C, 80°C and

200°C (autoclave) , which means that the novel matrix is useful for traditional low temperature curing, heat curing, and autoclave treatment. Heat curing (which in normal concrete leads to sHghly smaHer strength than curing at low temperature) probably seems to be the most promising curing technique for the material of the present invention.

O PI IPO

In accordance with what has been stated above, the volume of Hquid incorporated in the process is preferebly so that sub¬ stantiaHy no Hquid escapes from the mass during the shaping process , which results in several advantages in comparison with known processes where Hquid, typicaHy water, is removed from the sludge during the shaping process , typicaHy by some kind of filter pressing operation .

While the process of the invention can be said to constitute co - pletely new technology, it can also be considered as a valuable modification of existing technology . For example in the preparation of fiber cement products according to the Magnani process, shaping (from a dHute cement/fiber /water slurry) through rolling is performed, with concomitant removal of water by suction . When incorporating ultra fine particles and the extremely high amounts of dispersing agents in the mass to be processed in accordance with the principles of the present invention, these known tech¬ nologies can be modified to produce, by extrusion or rolling at a

2 shaping pressure of up to 100 kg/cm , an (even more dense) material from a viscous/plastic mass which already shows the final low water content so that no water or substantiaHy no water is removed from the mass during the shaping process , and hence, no suction arrangement is required.

As indicated above, additional bodies D may (like the bodies C and, to a certain extent, the bodies B) be incorporated at various stages during the process , and these additional bodies D are of the various types discussed in great detaH in the preceding text, the only limitation being, of course, that some type of additional bodies such as reinforcing bars or tendons in prestressed concrete can only be incorporated during the casting stage and not in any previous stage .

Unique . improved possibilities of submersed, in particular under- water construction comprise pouring a cement paste, mortar or concrete of the type of the present invention in the form of a coherent mass into a Hquid, typicaHy into water in the sea, a

harbour or a lake, and aHowing the mass to displace part of the Hquid and arrange itself as a coherent mass .

Other possibilities of utilizing the extraordinary shapeabihty pro- perties of the viscous to plastic mass are to shape articles by spraying, painting, or brushing to shape layers on other articles or to shape an article layer by layer, injection or simple hand - apphcation of a layer of the mass on a surface and conforming the mass to the shape of the surface. Centrifugal casting technique is another attractive shaping method useful in connection with the process of the invention.

In the same manner as disclosed in International Patent AppHcation No. PCT/DK79/00047, the articles of the present invention may be further subjected to impregnation to further increase their strength and improve their properties . The preferred materials and methods for performing the impregnation are the same as disclosed in International Patent AppHcation No . PCT/DK79/00047. A special feature of the present invention is the preparation of ultra strong DSP matrices by exchange of inter-particle Hquid in pre-arranged systems , such as is described in greater detaH in the foHowing section "HIGH RESISTANCE, ULTRA STRONG DSP MATERIALS" .

When the particles A are to be densely packed in the materials of the present invention, they are preferably of a size of from 200 A to about 0.5 μ .

WhHe particles A used in the Examples were SiO„ particles formed from vapour phase (in connection with the production of siHcium metal in an electric furnace) , also other ultrafine SiO„- containing particles may be used, in particular the particles mentioned in International Patent AppHcation No. PCT/DK79/00047. However, also-.in connection with the present invention, the particles formed by growth from a vapour phase are preferred.

Casting Adjacent to or Between Surfaces .

A novel appHcation of concrete, mortar and similar materials has been made possible with the extremely strong, room temperature- moldable materials of the present invention and of International

Patent AppHcation No . PCT/DK79/00047, namely the molding of articles with an external sheH and an internal part which is totaHy or partly fiHed with the strong materials of the present invention and of International Patent AppHcation No. PCT/DK79/00047 (concrete, mortar, paste etc. , reinforced or non-reinforced) .

This makes it possible to combine desired specific surface pro¬ perties of the articles (chemical, optical, thermic, mechanic, magnetic etc. ) with good bulk properties (especiaHy high mechani- cal strength and rigidity) and simple preparation technique (sepa¬ rate preparation of . sheH with subsequent introduction of flowable concrete, mortar or paste) . This constitutes a particular aspect of the present invention .

There is a number of advantages and potential advantages associ¬ ated with separate preparation of hoHow sheHs which are comple¬ tely .or partiaHy fiHed with the materials of the present invention and of International Patent AppHcation No . PCT/DK79/00047:

1. The preparation of the surfaces (sheHs) of the articles may take place independently of the preparation of the in¬ terior load-bearing reinforced core, that is , in environments (with respect to temperature, pressure, exterior f acuities , etc . ) which are not limited by requirements imposed by the interior core (extrusion of plastic, preparation of glass or ceramics sheH, etc. )

_ 2. Very large thin-waHed members with monohthic reinforced load-bearing core may be prepared. For example, it is possible to produce long stretches of tubes with monohthic strong reinforced core in the tube waHs (for example, in connection with lines on the sea floor where tubes having

hoHow waHs of plastic or the like are correctly positioned, the interspace being fiHed with stone and reinforcement, whereafter the tubes are fiHed with paste or mortar according to the disclosure of International Patent AppHcation No. PCT/DK79/00047 or according to the present invention by injection) .

Other members which may be prepared in this manner are ship huHs , large buHding sections , tunnel linings and the like.

3. The mold work is simpler than in constructions where the load-bearing reinforced concrete or mortar is first produced in a special mold and is thereafter provided with the surface materials . In accordance with the principles of this aspect of the present invention, the surface coating functions as shuttering .

STRUCTURE FORMATION

Curing Contraction of Portland Cement-based DSP Matrices .

On soHdification of the cement-based DSP material, a volume contraction takes place as is the case with ordinary cement paste.

The volume contraction is considerably higher for the new binder material, 2% against 0.5 - 1% for ordinary cement paste . This contraction may result in undesirable crack formations and change of shape.

The volume contraction is due to the fact that water is being consumed during the chemical structure formation and that the reaction products formed have a s aHer volume than the compo¬ nents from which they are formed. This results in internal cavita- tions and thus internal Hquid menisci, causing tensHe stresses in the Hquid phase which compress the powder mass . The finer the powder material the higher the meniscus-determined tensHe stresses

O PI

and thus the contractions forces . Therefore, when using powder which is 50 - 100 times finer than cement, considerably stronger contraction force prevail than in ordinary cement paste.

This is , e . g. , known from draining out of soH, where fine clay shows a distintive volume contraction, whHe coarse sand does not substantiaHy change its volume. The volume contraction is also strongly dependent on the hydration products formed, e . g. , calcium siHcate hydrate, during the hardening, especiaHy their abiHty to create internal contraction stress when less strongly bound water is moved for being consumed elsewhere in the hydration process .

Various precautions may be used or contemplated to reduce or eliminate the volume contraction of the binder, reduce the volume contraction of the composite material and/or reduce or eliminate possibly damaging effects of the volume contraction of the binder - especiaHy crack formation.

1) changing the interface tension between Hquid and gas and/or between Hquid and sohd in order to reduce the gas- Hquid-surface tension and/or increase the contact angle in order to decrease the contraction forces . This could be obtained by adding surface active substances or by changing (increasing) the temperature.

2) Adding Hquid as compensation for Hquid consumed for chemical reaction . The Hquid is added from outside to the surface of the article or from inside through channels from an external source or from internal sources , where the Hquid may be present in the Hquid state (e .g. in porous sand or stone grains or fibers) or in the sohd state (e . g. as ice - - which melts later) or chemicaHy bound (so that the Hquid is e .g. released on chemical or thermic influence) .

3) Changing (increasing) the volume of the pore Hquid and thus compensating for chemical loss of Hquid, e . g. by heating.

(NormaHy, the thermic volume changes of Hquids are con¬ siderably greater than those of soHds) .

4) Reducing the volume contraction of the composite material by using a dense packing of rigid coarse particles - typicaHy sand and stone . Thus , the volume contraction in mortar and concrete wiH typicaHy be reduced to 1/10 compared with the pure paste.

5) Impeding formation of internal cracks caused by contraction tendency by

a) increasing the energy required for opening a crack, e. g. by using sharp-edged sand and stone materials and/or fibers and other reinforcement (the inventor has successfuUy used fine woHastonite fibers, various glass fibers, steel fibers and plastic fibers) ,

b) increasing the rigidity of the composite material e . g. by using dense packing of sand and stone.

(The background of both of these measures is to be found in fracture mechanics, as, according to linear elastic fracture mechanics, the rupture tension is proportional to the square root of the cracking energy multipHed by the modulus of elasticity . )

c) the incorporation of bodies , which, due to their size, shape, or surface configuration could function as internal crack initiators and could act as guides for already formed cracks , such as would be the case with, e . g. , large bodies with sharp protruding corners and smooth

- -. surfaces .

6. Avoiding that the member, during curing, is exposed to damaging tensHe stresses . This may e . g. be obtained by curing in a compression stress field and/or by securing a

uniform contraction of the article e . g. through appropriate mold design (including use of flexible molds of rubber and simHar materials) .

7. Creating a more volume-stable chemical structure of the hydration product, e.g. , by incorporating more calcium-rich ultrafine particles such as calcium carbonate particles, in accordance with what is described in the foHowing section "Use of Ultrafine Particles to Improve the Chemical Structure of DSP Materials" .

8. By heat-curing (low pressure steam curing or autoclaving) .

9. By use of components which consume less water during the hydration process , e .g. by utilizing cements with less than normal C„A content.

10. By using expanding agents , such as aluminum powder, which wiH compensate for the contraction by an expansion proceeding simultaneously with the contraction. Also, other typical cement-expanding agents may be used.

Use of Ultrafine Particles to Improve the Chemical Structure of DSP Materials .

A particularly useful form of DSP materials comprises particles B and A, where the structure formation takes place by partial disso¬ lution in a Hquid and precipitation, the particles B being the more reactive . TypicaHy, particles B are Portland cement (d ~ 5 μm) and particles A are siHca dust (d "* 0. 1 μm) .

The 'dense DSP-structure is shown in Figs . 1 and 68.

On structure formation, a new structure is formed which glues to¬ gether the remaining parts of the original particles (probably the major part) , which results in a coherent structure .

It is desired to control this structure formation, both on coHoidal level (i. e . how the gluing material is distributed in the particle A space, whether uniformly or concentrated in the neighbourhood of particles B) and on atomic level (i. e. how the chemical structure is constructed) .

As an example it might be interesting to consider a system of Portland cement and siHca dust (typicaHy with mean particle sizes of 5 μm and 0.1 μm, respectively) arranged according to the prin¬ ciples for DSP-materials (vide Figs . 1 and 68) .

The sohd structure is based on a combined cement- water- reaction and cement- water- sHica- reaction wherein

1) material from the siHca dust to a larger or smaHer extent (by dissolution and reaction) forms part of the formed sohd calcium siHcate hydrate structure.

2) The distribution of the calcium siHcate hydrate throughout the space between the remaining sohd particles is not beHeved to be uniform, typicaHy, there is a higher concentration near the sur¬ face of the cement particles (the cement being typicaHy the main producer of "structural material") . Thus , it is Hkely that volumes in the interior between the cement particles (vide the circle in Fig. 68) may suffer from shortness of calcium siHcate hydrate and therefore may be impeded from gluing the remaining siHca particles in a very dense structure.

3)_ It is also Hkely that the distribution of elements in the chemical structure formed is uneven, typicaHy with a higher concentration of calcium in the neighbourhood of the cement particle surface and a surplus of siHcium in the calcium siHcate hydrate formed in the space occupied by silica dust.

OMFI

WIPO

It is desired to control the structure and the structure formation in detaH, which means increasing the amount of structure formed in the siHca particles' interspace structure, also in a greater distance from the cement surface and introduce a high degree of calcium control with respect to the calcium siHcate hydrate formed.

According to the invention, the missing elements (or other desired elements) are added to the fine particles , typicaHy in the form of other fine particles .

Thus, a natural measure to solve the problem would be to add ultra fine Portland cement to the fine siHca, i. e . , to replace 20 - 80% of the siHca with ultra fine cement which is typicaHy 2 - 10 times finer than the Portland cement or even more .

This measure considerably decreases the size of the micro volumes fiHed with siHca dust, typicaHy a reduction by a factor of 2 to 10 or even more.

However, this procedure has two drawbacks

1) the very fine reactive cement may cause production trouble by too fast chemical reaction (stiffening effect) . (This effect is , how¬ ever, not always undesired, as it may be used in a controUed fast setting, which is highly desirable . )

2) The very fine reactive particles may dissolve completely with the result that they do not participate in forming the desired ideal particle based structure.

According to an embodiment of the present invention, ultra fine particles A are used as a calcium source which is a far less reactive form than cement, e .g. by using coHoidal calcium car¬ bonate (particle size typicaHy below 0.5 μm) in the Portland cement siHca system . Calcium carbonate would normaHy be con- sidered very sparingly soluble in water and is slowly soluble when used in larger grain form, but due to the large specific surface (typicaHy 10 - 1000 m ² /g) , the solubility and the rate of the solution are increased, which makes it possible to combine the

/- O R AD

desire to preserve the particles during the first few hours after mixing with water (partly adjusted by surface- active agents) and the desire of reasonable reactivity with water and neighbouring particles of SiO _? during the hardening.

The system behaviour may be improved/optimized by several means :

1) geometrical balance, i. e. , arranging ultra smaH Ca(CO ₃ ) ₂ par¬ ticles (d ~ 0.01 μm) in the space between the silica particles .

2) Using extremely smaH Ca(COo) ₂ -particles , hereby increasing the solubHity of the Ca(CO,,) ₂ (according to thermodynamics of smaH particles) . The benefit of this effect requires particles which are typicaHy below 100 A (diameter) , preferably below 20 A, e . g. smaUer than the particles A .

3) Using means to change the solubHity (increased or decreased temperature) or change in chemical composition of the Hquid, i.e. , a solution of CO„ in water strongly increases the solubHity of Ca(CO ₃ ) ₂ .

Hence, an embodiment of the invention comprises incorporating calcium carbonate particles having a size of from about 20 A to about 0.5 μm among the particles A. The ratio between the calcium carbonate particles and the sHica dust may vary within wide limits , such as between 1 :99 and 99 : 1.

APPLICATIONS

Due to its extreme tightness and mechanical strength, the material made possible by this invention is useful in a wide range of ar¬ ticles , examples of which are a sheet or panel of thin-waHed plane or corrugated shape, such as sheets or panels of the same shapes as the known art asbestos cement products; a pipe; a tube ; a re¬ fractory Hning (e.g. , appHed as a complete Hning) or a refractory Hning component (such as a building stone for a refractory lining) ; a protecting cover (e . g. to protect other materials

influences) such as a cheap protecting cover appHed on steel, e . g. steel tubes or pipes , or on ordinary concrete products so as to supply concrete products with a noble surface w ^τ hich is strong, abrasion resistant, and acts as a sealant against influence from the surrounding environment, protecting covers on masonry, pavements and roads , utilizing the same beneficial characteristics of the novel material, and protecting covers on roofing panels or tiles , or on containers; a roofing material such as a roofing panel or tile; an electricaUy-insulating member; a nuclear shielding for protection against radioactive action (for radioactive-based reactor construc¬ tions, etc. ) a seafloor structure for deep water appHcations ; a machine part; a sculpture; a container; an in situ cast oH weU waU; or a load-bearing member in structural engineering utilizing the extreme strength quaHties of the material and its resistance to climatic influence, such as a beam, a sheH, or a column , typicaHy as reinforced concrete, especiaHy as pre-stressed concrete .

Seafloor structures for deep water appHcations , e .g. spherical containers to withstand large hydrostatic pressures require concretes of a high strength, high durability and low permeability .

"Polymers in concrete" , ACI PubHcation SP-40-1973, P 119-148, report model tests on smaH 16 inches diamether spherical huHs made of high quaHty polymer-impregnated concrete for deep water appHcations . FuH impregnation was obtained by a compHcated drying- vacuum outgassing-pressure procedure which is , in practice, Hmited to smaH size members . With the materials and processes according to the present invention, it is now possible to produce such struc¬ tures in large scale (several meters in diameter) with a similar high quaHty material by a simple fabrication technique .

Some examples of appHcations of the DSP materials have already been given . Other examples are the foHowing structures which may be produced by casting adjacent to or between surfaces :

OMPI

Large electric insulators are today made from glass or ceramic ma¬ terials, especiaHy because of the exceHent insulating properties of these materials . It is of special importance to prevent currents along and in the surface layers . Besides , large insulators demand high mechanical strength and a good ability to absorb mechanical energy. This is difficult to obtain with brittle materials such as glass and ceramics to which it is difficult to impart "toughness" by reinforcement (due to the fact that they are shaped from fluid masses at high temperatures and sohdify under relatively great volume changes) . However, in accordance with this aspect of the present invention, high material strength and good ability to absorb mechanical energy may be obtained in such large electrical insulators by producing large hoHow jackets or sheHs of glass or ceramics which are fortified with reinforced high quaHty DSP concrete, mortar or paste prepared by casting of soft mass

(injection, etc. ) ; the reinforcement may be placed in advance in the interior of the jacket or sheH (large steel bars , etc . ) , or the reinforcement may be part of the casting mass (e.g. chopped fibers) .

It is contemplated that this WTH make it possible to realize a cheaper production of large insulators in the sizes in which they are produced nowadays , and to produce far larger insulators than those known today.

Furniture , shelves , doors etc . , which, due to requirements concer¬ ning appearance, tactile sensation, cleanabiHty, chemical durabHity, etc . , require special surface properties combined with good mecha¬ nical bulk properties (strength, toughness) may be prepared from hoHow members of plastic, metal and the like (e . g. prepared by extrusion) which are fiHed wάth a reinforced DSP binder by pouring, injecting etc.

Strongboxes and other strong containers which may be produced by filling the cavities in doors and waHs with the DSP material by casting of soft mass (injection etc. ) ; aU or parts of the internal reinforcement and hard components (e . g. bauxite stone) may be placed in advance.

OMPI A WIPO

Containers for radioactive waste in which the radioactive waste is cast into the above-mentioned strong materials , by injecting a paste or mortar of the DSP materials into the container room in which aU or part of the reinforcement, the radioactive waste in sohd form and various rigidity-imparting elements (e . g. bauxite stones) have been placed ^" in advance .

Very large sculptures of desired surface materials , which in an inexpensive way may be given the required mechanical strength by filling a thin sheH with reinforced mortar or concrete prepared according to the principles mentioned in the previous examples .

Load-bearing constructions with special requirements for surface materials (pHlars , waUs , floors , roof elements etc. )

Ship huUs with an exterior and an interior of materials with special properties (e.g. smooth exterior and heat insulating interior) where the necessary part is fHled with reinforced DSP concrete, mortar or paste by injection etc.

Tubes with an exterior and an interior comprising materials with special properties (e . g. acid resistant interior and heat insulating exterior) where the interspace between the tube waUs is fHled with reinforced DSP concrete, mortar or paste by injection etc .

As mentioned above, there is a number of advantages and potential advantages associated with separate preparation of hoHow sheHs which are completely or partiaHy fiHed with the DSP materials . In this connection, it should be emphasized, e . g. , that very large thin-waHed members with monohthic reinforced load-bearing core may be prepared. For example, it is possible to produce long stretches of tubes with monohthic strong reinforced core in the tube ^" waUs (for example, in connection with lines on the sea floor where tubes having hoHow waUs of plastic or the like are correctly positioned, the interspace being fHled with stone and reinforcement, whereafter the tubes are fHled with DSP paste or mortar by injection) .

Other members which may be prepared in this manner are ship huHs, large buHding sections , tunnel linings and the like.

The possibility of producing, with a simple casting technique and at room temperature, reinforced concrete, mortar and paste with very high strength and acceptable toughness makes it possible to produce members which are traditionaUy produced of metal. Such members are in particular large load-bearing members traditionaUy produced as metal castings (covers , Hds , large valves , load- bearing machine parts , etc. ) and structural members (masts , beams, and the like) .

The high hardness of the DSP materials , combined with the fact that they can easHy be made tough through fiber reinforcement, makes it possible to use the materials as milling or grinding bodies and abrasion aggregates, typicaHy produced by ordinary casting of soft mass , extrusion, or compression.

In connection with the claiming of this aspect, the "substantiaHy uniform thickness" is not to be taken as a limitation to particular surface layers with very exactly regulated thickness . Rather, the "substantiaHy uniform thickness" is merely to be understood as a distinction from structures which can no longer reasonably be designated as surfaces or surface layers, such as a rock structure in which a cavity has been fiHed with the DSP mass .

The statement to the effect that the surface layer or layers should have a structure which is different from the structure of the cured mass cast adjacent to or between the surfaces is intended to reflect the fact that the exterior material is different from the interior material used in the particular case . It is absolutely not precluded that the type of material used for the exterior surface would be the same type of material as is used for the interior material, in other words , would contain a matrix of the same type .

Also in connection with the articles prepared according to this aspect of the invention , an impregnation of the interior material (and of the exterior surface material, if it is of the same general

^TJTE

type) may be a preferred treatment to further increase the the strength and durabHity, and any further impregnation treatment is performed in an analogous manner to the impregnation of the materials which are not molded between surfaces .

TOOLS AND MOLDS FOR SHAPING ARTICLES .

The typical DSP materials of the present invention have good strength, hardness , heat resistance and chemical resistance. These properties, combined with the fact that articles of DSP materials may be shaped by very simple processes - casting, vibration, vibrop res sing, rolling, etc. - and that the DSP articles reproduce, down to the last detaH, the surfaces against which they are cast, render them extremely weH suited as tools and molds for shaping articles by deformation processes .

For many appHcations , special DSP materials may be used, where specific properties such as ultra-high heat resistance and high heat conductivity is required.

A wide variety of materials may be shaped using tools and molds which are completely or partiaHy made of DSP materials . As examples of materials which may be shaped may be mentioned steel, aluminum, ceramic materials such as Al _? O,,, gypsum, cement pro¬ ducts , including DSP materials, organic materials such as plastics , wood, etc.

The materials which are shaped using DSP molds or tools may be in various forms such as soHd, Hquid or gas form or combinations hereof, with correspondingly varying mechanical properties ranging from, e. g. low viscosity at casting with Hquid metal to high yield or ^' flow stress at powder compaction or at bending or drawing of steel panels .

The shaping temperature may vary over a very large range from OK to several thousand centigrades, and the pressure may be varied over a wide range from 0 to more than 1000 MPa.

In many cases, the DSP mold or tool material is advantageously made with a binder of Portland cement and ultrafine particles which are from one to two orders of magnitude smaHer than Portland cement, typicaHy siHca dust.

When extreme thermal, chemical or mechanical influences are en¬ countered during operation, of the DSP molds or tools, other com¬ ponents of the DSP binder wiH be taken into consideration, such as refractory cement based on DSP binder or plastic-based DSP binder - the latter typicaHy to increase acid resistance, or the DSP tool may be constructed from materials with a binder of Port¬ land cement reinforced or protected at particularly exposed places by means of other materials, such as materials comprising strong bodies C, or by means of incorporated large bodies of special properties, such as steel hard metal, polytetrafluoroethylene, etc.

The tools or molds may be of wide varying design, ranging from containers in which a casting mass is fed to the orifice of an ex¬ truder, to a compression piston or patrix. In aH the cases it is characteristic that the surfaces of the tool or mold wiH, to a greater or lesser extent, be reflected in the articles produced.

One type of shaping process performed in molds of DSP material is Hquid casting where the material which is to be shaped is placed, in Hquid form, within the mold limitations. Liquid casting may be aided by other means such as pressure (pressure casting) , vacuum

(vacuum casting) , forces of inertia (such as in centrifugal or rotational casting) , vibration, and heat.

A special form of Hquid casting is sHp casting where the material to be shaped consists of soHd particles and Hquid, usuaHy water, where the casting in molds of a compHcated geometry necessitates the use of a surplus of Hquid to render the mass fluid. During the casting, the excess Hquid is removed by being ^{^} expeHed through

T& OMPI ^{' '}

the surface of the mold, possibly aided by pressure, vacuum or forces of inertia. One advantage of selecting DSP materials for the shp casting molds is that it is easy to introduce, during the pre¬ paration of the mold by casting, channels or ducts securing the desired expulsion of Hquid (draining system) , and any assisting means necessary (e .g. vacuum ducts) .

In Hquid casting, the DSP mold material wiH, in principle, function like a casting mold or part of a casting mold. The DSP materials wiH normaUy be completely ideal for this purpose because they are easHy shaped in the desired configuration by casting around a prototype or a model of the article to be produced. When the DSP material is a Portland cement-based material, this casting may be performed at room temperature.

In heat casting, where the starting material is to soHdify during the casting, it may be essential to be able to control the tempera¬ ture at the surface of the mold, for example through securing a fast heat transport from the casting mass to obtain a fast sohdi- fication, either to ensure a high production capacity, or to influ¬ ence the structure of the cast material (quenching) or alternatively to secure a slow heat transport in order to obtain particular struc¬ tures in the cast material (e . g. to avoid thermal stresses) . With the DSP materials , it is possible to select suitable, individual material components adapted to their particular heat transport function in the tools or molds or parts thereof (e .g. by including heat insulating or heat conductive particles C to obtain controUed variations of the heat transport) .

Also, as mentioned above, it is easy to estabhsh, in DSP molds , cooling or heating or sensing components , e . g. thermocouples , thermosensors , zener diodes , heating resistors , etc . , in the molds , or- to incorporate ducts , tubes or channels for electrical heating threads and thermosensors . Furthermore, it is possible to intro- duce, in the DSP molds , means , such as channels , reservoirs , etc. , for controUed introduction of lubricating substances during the casting or shaping operation.

Compression or compaction of masses of a plastic character such as steel panels so that the masses wHl completely or partially fiH a defined space is another shaping technique . For this purpose, the DSP materials are suitable both as the patrix and matrix part of the tool. An example of such a tool is a press-tool of Portland cement-based DSP with particles C of refractory grade bauxite for shaping this steel, such as automobHe body parts as Hlustrated in Figs . 38 - 40.

Also the compression shaping process may be aided by vibration, vacuum, heat, etc.

In extrusion shaping, a blank having a constant cross section is pressed out, in plastic condition, through a die orifice.

The plastic deformation takes place in the extruder chamber and the die orifice. Both of these components may advantageously be made from DSP materials . Also in this case, the possibiHty of introducing, during the casting of the DSP material, various com- ponents in the extruder chamber and shape- defining means , com¬ ponents for regulating heat, lubrication, etc. , is of great advan¬ tage.

If it is desired to introduce special components , e .g. steel fibers or other materials, at special positions in the extruded article, such components may easHy be introduced through ducts in the extrusion mold.

Often, the design of an extrusion chamber is particularly complex, however, the easy shapeabHity of the DSP materials greatly enhance the possibility of producing extruder chambers in an easy way . One particularly advantageous way is to cast a DSP material against a membrane maintained in the desired configuration by hydrostatic pressure balancing, such as Hlustrated in Figs . 34 - 36 , which are to fulfil extreme requirements with respect to performance may be made or coated with, high-quaHty DSP materials made by designed arrangement of fibers and particles in a low stress field and ex¬ change of interparticle material by infiltration such as described in

the section "HIGH RESISTANCE ULTRA STRONG DSP MATERIALS" . Tools made of DSP materials may be tools which are driven by motor forces of any kind, but they may also be hand tools such as hammers , files , abrasion tools , etc. , where the special properties and design possibilities offered by the DSP materials are utilized.

MOLDS FOR POLYMERS

Molds for polymers are conventionaUy made by machining in steel.

This is normaUy expensive and time-consuming. Therefore, low cost molds for polymers have also been developed in the known art. Such low cost molds are made, e . g. , by machining of easHy machinable metals such as aluminum and magnesium, by casting polymer composits based on epoxy, polyester or polyurethane con¬ taining fillers of metal powder, often aluminum, by casting of aHoys usuaHy based on aluminum and zinc, or by means of metal-sprayed sheHs .

With the DSP materials , e . g. Portland Cement-based DSP materials, it is possible to produce molds which in many respects have the quaHty and performance of machined steel molds , but which in at least one respect are far better, namely with respect to their capa- bihty of reproducing a prototype of the article to be cast. Due to the capability of the DSP materials to reproduce even the smaHest details of a surface against which the DSP material is cast, such as even finger prints on a plastic surface, the shaping surfaces of molds of DSP materials may be provided simply by casting the DSP material against a prototype of the article which is to be mass-pro- duced in the DSP mold. In this manner, a mold for polymers can be produced at very low cost compared to the expensive machined steel molds , and with surface properties corresponding to any desired surface quaHty of the mass-produced article . (For example, when the article to be mass-produced from polymer is to have a pohshed surface, the prototype against which the DSP mold is made is provided with a correspondingly poHshed surface before the DSP mold is manufactured by casting of DSP material against the original) .

OMPI

Another advantage of DSP as material for making molds for poly¬ mers is that the cost of the material is lower than the cost of mold quaHty steel and that the manufacturing of the molds is much easier .

The surface of DSP materials may be designed so that it is readHy workable, which can be utilized in cases where it is desired to estabhsh special patterns or configurations, protrusions, cavities, etc. in the DSP mold surface. This is typicaHy done by incorpor- ation of a high concentration of very fine fibers , i. e . by the technique described in the section "HIGH RESISTANCE ULTRA STRONG DSP MATERIALS" .

Molds of DSP materials comprising a binder of Portland cement and siHca dust and preferably comprising strong bodies C may be made with compressive strengths of 130 - 260 MPa (the latter value being higher than the yield strength of soft steel which is typicaHy 210 MPa) and tensHe strengths of 10 - 20 MPa (which may be con¬ siderably increased by reinforcement with bars or fibers) . These DSP materials are very rigid with an elasticity of 50,000 - 90,000

MPa, which is between 1/4 and 1/2 of the elasticity of steel.

The DSP materials operate with retention of the above-mentioned properties in the entire temperature range required in polymer shaping.

The thermal conductivity of the DSP molds may easHy be adjusted by the use of insulating sand and stone if low thermal conductivity is desired, and by the use of thermaUy conductive particles (metals if high thermal conductivity is desired.

Due to the ease with which DSP materials are cast it is very easy to -estabhsh ducts or channels for cooling or heating, etc . , and to introduce, e.g. thermosensors in the DSP mold bodies during the casting thereof .

77

Compared with conventional low cost molds for polymers (Reference 44) the molds made from strong DSP materials offer the foHowing advantages :

1) Compared with machining in metals :

The DSP molds are produced in an easHy workable material. Molds made from DSP based on Portland cement and siHca dust can retain absolutely satisfactory mechanical quaHty over the entire temperature range which may be encountered in the molding of polymers . They may be shaped in far more compH¬ cated shapes than the conventional low cost molds , and they may precisely dupHcate even the s aHest detaH in the articles to be shaped. The molds may be made in very large dimen¬ sions , which makes it possible to produce very large bodies by molding of polymers , such as shiphuHs , buHdings , auto- mobUe bodies, large pontoons , etc.

2) Compared with molds cast from- polymer composites : Molds made with strong Portland cement DSP materials contain- ing strong bodies C show better mechanical properties than the polymer composite molds, especiaHy for high temperature polymer shaping. Also, the DSP molds are made without the health hazards associated v/ith the casting of polymers such as epoxy.

3) Compared with molds made in metal casting: The DSP molds also have better mechanical properties at high

^' temperatures than molds made of zinc or aluminum. As the DSP materials show smaHer hardening contraction than cast metal, it is possible to make DSP molds which can be used in precision shaping (which is not possible with metal cast molds) .

4) Compared with sprayed sheUs of metal:

The DSP molds may be cast at room temperature, thus without danger of damaging the model, and they have higher mechan¬ ical resistance than the sprayed sheHs of metal. On the other hand, if desired, DSP materials could easHy be appHed as backings on sprayed sheHs of metal.

OMPI

CASTING

On several occasions within industry, archeology, construction, natural history, etc. it is desired to copy a sample in such a manner that its shape and surface structure is preserved and maintained in a rigid, durable structure, the surface of which reproduces (often to the smaHest detaH) the surface and shape of the sample .

In a number of fields , DSP materials are exceHent for such pur¬ poses , and in certain appHcations , they even permit the preserva¬ tion of shapes and surfaces where this has previously not been possible by any casting technique.

Casting is typicaHy performed by shaping the casting mass in fluid or plastic or other defor able condition over the surface of the sample - or the part of the sample - the shape and surface of which it is intended to reproduce/ and thereafter soHdifying the casting mass to a mechanical soHdity which permits removal of the sample with retention of the copied shape .

1. DSP casting mass may be completely easHy flowing with typical Hquid behaviour (filling even the smaHest surface irregularities and s elf -le veiling) , or tough and plastic and suitable for shaping by compression against the sample, or in loose form which, by impact against the sample, is assembled into a coherent mass, such as by injection moulding.

2. DSP casting masses are able to reproduce extremely fine details in the micron range, e .g. , fingerprints on a plastic surface .

3. DSP casting masses show good volume stability on hardening. The volume stabiHty may be increased by stabilization by means of a high volume content of additional bodies, such as sand, stone, fibers, reinforcement, etc . , in the DSP paste (which consists of

Hquid, particles A , and particles B) .

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4. DSP casting masses may be shaped over a broad temperature range . Portland cement-water based DSP material may be used without compHcations of any kind at temperatures from 0°C to almost 100°C (referring to processing at atmospheric pressure) . By use of autoclave technique, the range may be expanded to far beyond 200°C .

5. DSP casting masses may be shaped over a broad pressure range, thus permitting casting under ordinary atmospheric conditions , under vacuum conditions, e . g. , lunar castings, and under high pressure conditions (e . g. , deep sea castings) .

6. DSP casting masses may be shaped to articles having very high mechanical strength, the compressive strength is typicaHy 100 - 160 MPa and strong sand and stone such as the strong materials mentioned 180 - 280 MPa. The tensHe strength and ductiHty may be strongly improved by fiber reinforcement.

This permits preparation of very large casts (several meters) where the known art technique permit ^' s only partial castings with the consequent difficulties in rearranging the single parts into correct position .

7. DSP casting masses are especiaHy weH suited for shaping under water, where the material, as a coherent mass, displaces water

(due to the higher density) and effectively fiHs any cavity to be fHled. The casting of DSP materials under water to effectively fiH any cavities constitutes a completely new technology with very broad-spectered utility.

8. The DSP casting mass wiH normaUy not incur any chemical damage on the surface to be reproduced. If, on the other hand, there would be a potential risk for such damaging, the surface could be protected through a surface treatment.

9. In many cases, the DSP casting mass wiH not adhere to the surface. However, where there is a potential risk or such ad¬ hesion, the surface may be modified to counteract it, e .g. by means of surface active agents , or by film coating of the surface, or the DSP casting mass may in itself be designed so that it shows suitable release properties .

10. Due to its very good flowabUity, the DSP casting mass may be brought to exert only very gentle influence on the samples to be reproduced, corresponding to the case where the only influence is the hydrostatic pressure of the fluid DSP mass . In cases where it is desired to reproduce a very easHy deformable surface, the effect of umlateral hydrostatic pressure (deformation or crushing) may be balanced be estabHshing identical hydrostatic pressure at the opposite side of the surface according to the principle of com¬ municating vessels . This technique is especiaHy weH suited for casting where the shape of membranes is to be preserved.

Performing the Casting.

The casting may be performed in many ways :

1. Filling of cavity with DSP materials of Hquid fluidity simply by pouring the DSP material into the cavity, preferably from below or through a tube which extends down to the bottom of the cavity.

2. Filling of cavity with DSP material of Hquid fluidity under water (or under another Hquid) by pouring, again preferably from below or through a tube extending down to the bottom of the cavity. '

3. Filling as under 1 and 2, but aided by pressure, vibration, or centrif ugation .

81

4. Filling as under 1, 2, or 3, aided by vacuum to remove air in any cavity (1) or in the casting m^ss (1, 2, 3) .

5. Prearrangement of additional bodies C (fibres, reinforcement, sand, stone) , relevant in any of the methods 1, 2, 3, and 4.

6. Filling of cavity with deformable surface, typicaHy membranes , with retention of the shape of the surface by estabhshment of identical pressure on the opposite side (by means of DSP material or other Hquid having a suitable density.

7. In a manner corresponding to 6, but using injection casting technique .

8. Casting of a surface with plastic DSP casting mass (optionaHy fiber- supported) which is pressed against the surface, optionaHy aided by vibration. In this technique, the material may be aUowed to harden whHe in contact with the surface, or the plastic material may be removed from the surface immediately after the pressing. In this case, release agents may be used to assist in the removal of the material.

AppHcations of the casting technique.

The casting technique described above is useful in a great number of appHcations, typical examples of which are:

1. Archeology, where especiaHy very large casting and, in parti¬ cular underwater castings may be made which where not hitherto possible, one special example being casting under extremely deep water .

2. The reproduction of the shape of automobHe body parts and other parts of shaped metal.

82

3. The reproduction of the shape of construction members .

4. Through casting against deformable surfaces (through hydro¬ static balancing) , it becomes possible to cast very large, extreme elegant structures .

SURFACE COATINGS

The present invention also relates to the utilization of DSP mate as surface coatings .

The DSP materials show unique properties as surface coating materials due to their combination of dense and ultra fine structu which results in a strong, dense and diffusion- tight coating on substrates . With respect to appHcation properties , the easy flowabiHty and deformabiHty of the DSP materials secure an easy appHcation of the DSP materials and conformation of the DSP materials to the substrate on which they are appHed. This permit the use of traditional techniques for pain ting , and coating in con¬ nection with DSP materials , including brushing, spraying, rolling high pressure spraying, "airless" spraying and, pouring, doctori stopping, and filling.

The above principles can be generalized into principles where the material flows onto the substrate by gravity and surface forces (the ideal is that the film of the DSP paint or coating appHed should be capable of effectively wetting the substrate) , and anot principle is combination of the coating and the substrate aided b mechanical means (this includes brushing, stopping arid filling, also including vibration utilizing the beneficial effect of the vibra tion on the particle orientation) .

The structure of the DSP material is unique due to the particular structure of the material consisting of densely packed particles B with homogeneously arranged or densely packed particles A. In many cases , it is desired to impart tensHe resistance to coatings . In this respect, it is useful to employ fibers . The size, shape,

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and amount and type of fibers are strongly related to the require¬ ment w ^τ hich the coating is to fulfil and to the dimension thickness of the coating. With speciaHy thin paint film, typicaHy below 1 mm or better below 0.3 mm, it is desirable, in accordance with fracture mechanics, to use ultra thin fibers , preferably in the range from 10 micron to 0.1 micron . In the DSP materials , it is now possible to obtain effective anchoring of such ultra fine fibers . Such an¬ choring of ultra fine fibers has not been possible in previous sur¬ face coating or paint materials .

Due to the dense packing of the particles B and optionaHy the particles A, the DSP materials wiH, other conditions being equal, have higher abrasion resistance than conventional comparable ma¬ terials . Special improvements of the abrasion properties of the DSP materials can be obtained by including the types of bodies C men¬ tioned in Danish Patent AppHcation No . 1945/80, that is , particles C consisting of the materials characterized in claim 17 in Danish Patent AppHcation No. 1945/80, in particular topaz, lawsonite, diamond, corundum, phenacite, spinel, beryl, chrysoberyl, tourmaline, granite, andalusite, staurohte, zircone, boron carbide, tungsten carbide. One preferred type of particles C are particles C consisting of refractory grade bauxite. The particles C may be present in the DSP material used as paint or surface coating material in a volume which is in the range stated in Danish Patent AppHcation No . 1945/80, that is , a volume which is about 10 - 90% by volume, preferably 30 - 80% by volume, and in particular 50 - 70% by volume, of the the total volume of the particles A, B and C.

The size of the bodies C or D may be adapted to the particular requirements concerning surface texture, and film thickness . Thus , the additional bodies C or D may be of sizes from 1 to 40 micron as -a typical range for ultra fine coatings (coatings having a thick¬ ness in the range of typicaHy 5 to 200 micron) , and the additional bodies C or D may have sizes going up to the order of centimeters, typical for coatings of large constructions , such as off-shore con¬ structions , oH tanks , etc.

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When the DSP materials are used as paints or surface coatings, they will often be used to obtain an ti- corrosion effects such as rust prevention, and for this purpose, it is of importance that cement, such as Portland cement, in itself shown anti- corrosion properties, in particular rust prevention properties when appHed on steel surfaces . Therefore, the DSP materials used as paints or coating materials wiH often comprise Portland cement particles as a major proportion of the particles B . In addition to the chemical rust prevention effects and other anti-corrosive effects exerted by the Portland cement particles, another interesting feature is that

DSP materials comprising Portland cement show a considerably reduced electrical conductivity as compared with normal cement materials , which results in improved electrical insulation of the articles coated and thereby reduced galvanic corrosion, etc.

Hence, preferred DSP materials for use as paint or surface coating materials are materials in which the particles B comprise at least 50% by weight of Portland cement particles . Preferred particles A are of the same types as disclosed in the above-mentioned Danish Patent AppHcation No. 1945/80. However, it wiH be understood that DSP materials useful as paint or surface coating materials are not Hmited to such constituents, and that the general principles for estabhshing a dense matrix such as disclosed in the above¬ mentioned patent appHcations may also be utilized in connection with the construction of paint or coating DSP materials comprising particles A and B of a different chemical nature, the nature of the particles A and B for any given DSP paint composition being dependent on the particular end use of the paint or coating com¬ position in accordance with general principles within the paint and coating composition art. Obvious embodiments within this aspect are embodiments where the particles B comprise or consist of pig¬ ments of the types which have been found useful within general paint- technology .

A factor which is of special importance in connection with the utility of a particular material as paint or surface coating compo¬ sition is the resistance of the composition against peeling from the surface of substrate on which it is appHed. In the foHowing, HE

factors influencing the resistance of DSP materials against peeling, partly in the cured state, and partly in the uncured state, wiH be discussed:

The resistance of a cured paint or surface coating against peeling is basicaHy a question of obtaining as large a work of separation as possible of the surface from the substrate. The work of separation depends on several factors , such as the binding force between the surfaces and the range of action of the force, or the direction in which the force exerts itself. Taking as an example a tape glued on a non-flexible surface, the ease with which the tape is peeled off depends on the work which is necessary to separate the tape from the surface. In this connection, a very important factor is the deformation of the surface being peeled off .

The work involved in peeling off is the integrated product of peeling force and displacement. For this reason, the foHowing factors increase the peeling resistance:

a) A good chemical bond between the coating and the substrate

(increases the force) .

b) As long a displacement as possible (a long range over which the adhesive forces are active, that is , e. g. , a bond constituted by molecules of sufficient lengths to exert plastic or elastic pro¬ perties in the separation zone) .

For this reason, it is preferable to include in DSP materials to be used as peeling resistant surface coatings , substances which, when the coating has set, may exert their forces in a peeling situation, e .g. , substances comprising molecules which are capable of attach¬ ing on the one hand to the substrate and on the other hand to be anchored in the coating, and molecules which are capable of con¬ siderable deformation before the attachment is broken, in particular "long" or "tangled" molecules of high molecular weight, including ionic polymers , siHca in polymeric form, including sHicones, sHanes and sHoxanes, polycarboxylates and change of den tin coUagen, etc.

86

Another factor which improves the peeling resistance of a coating is improvement of the molecular behaviour of the molecules of the surface coating. Factors contributing to a good bond in this rega are a beneficial texture of the surface where the DSP materials c benefit from the fact that they show degrees of roughness which are smaHer than any previously known level for simHar particle- based materials . (E .g. a matrix having an internal "roughness" o about 10 micron cannot anchor a 10 micron particle system, where the DSP materials having typicaHy particle A-sizes of 0.1 micron are capable of conforming to or filling roughness cavities in a 10 micron particles size system . ) The texture of the surface to be coated may be controUed or influenced by mechanical ways by brushing or grinding, poHshing, sand blasting, etc.

It is also possible to incorporate, between the surface to be coate or protected and the DSP material, an intermediate layer which is capable of adhering weH to both the substrate and the coating. Such a layer may in itself include properties resulting in a high work of separation, (cf. the above discussion) . The material may also be a material which adheres weH to the substrate and has a surface, e.g. a surface with exposed fibers , which results in an optimum anchoring of the DSP material. In case of very thin DSP coatings in the range below 1 mm, anchoring elements of fibers in such an intermediary layer should preferably be in the dimension of 0.1 - 10 micron diameter in order to yield an optimum anchorin with a DSP material. Obviously, it is also possible to use long "anchors" or "large" anchors, including fibers or fiber- like bodie which may be arranged either paraHel to the substrate or non- paraHel to the substrate, perpendicularly etc.

The resistance of a DSP material against peeling during curing or hardening is also dependent upon the work of separation . In this respect it may be favourable that the coating when appHed in uncured condition comprises a layer which has a somewhat lower concentration of the particles A adjacent to the surface to be coated .

With a lower concentration of the particles A immediately at the surface of the substrate, the strain capacity of the system when appHed wiH be increased, because crack openings in Hquid-bound saturated particle systems are roughly in the order of magnitude of the particle size as the particles are bound together with Hquid minisci which can be 1/5 - 1/3 of the particle diameter before breaking. (This is in accordance with the weH-known technique where, in order to connect old concrete with new concrete, thin water-rich cement paste is brushed over the surface (broomed finishing) . To the appHcants' best knowledge, the precise description of the beneficial effect of broomed finishing according to fracture mechanics has not been pubhshed) . The measures mentioned above for improving the adhesion of the hardened or cured surface layers to the surface can also be appHed in connection with improvement of the wet peeling properties . Much of the peeling occurs due to differential movement of the film, during hardening, drying, etc. The peeling off forces arise, to a high extent, due to differential movement of the upper layer compared to the lower layer in direction paraUel to the coating surface, which would lead- to a banana-shaped cross section if there were no peeling resistance. As the peeling resistance depends to a smaHer degree on the thickness , a decrease or lowering of the film thickness would be beneficial to reduce peeling in uncured state .

Due to their particular properties with respect to anchoring fine fibers and forming a dense and impermeable surface even in a very low thickness , the DSP materials provide a paint or coating mate¬ rials which are optimaHy adaptable to avoid peeling.

One method to counteract peeling in uncured state is to secure a sufficiently flowable or movable Hquid suspension of particles A which in itself is able to form minisci between the particles B and the substrate during any attempt of separation . This requires sufficiently easHy flowable or movable Hquid suspension of particles A which in itself is able to form minisci between the particles B

and the substrate during any attempt of separation. (This requires a not too high concentration of particles A in the fluid phase and furthermore that the particles A are considerably smaHer than the particles B , typicaUy at least 1, but preferably 2 orders of agni- tude smaHer than the particles B) .

In this connection, the DSP materials are eminently suited because of the construction thereof comprising the particles B with the particles A which are 1 to 2 orders of magnitude smaHer. Another measure for counteracting peeling is to render the Hquid phase capable of absorbing work to a higher extent, e.g. by incorporatin elements of long or tangled structure, e. g. polymer molecules, but also fibers which are of a size range down in the 1 micron range or lower or sub-micron range would contribute to this effect.

In addition to this , measures which tend to increase the strength of the paint or coating layer wiH also counteract peeling effects, including the appHcation of the DSP paints in several layers to obtain a high quaHty surface, etc. .

The DSP materials may be appHed as coatings or part of coatings by placing the material as a coherent mass , e. g. premixed, or by placing the various components separately, either in a specific order, e.g. first the Hquid and then the particles , or simultaneousl by simultaneous spraying of particles and Hquid, or any combinatio thereof may be used.

TypicaUy, the DSP material is premixed as a coherent very fluid heavy plastic mass and placed in position on the surface to be covered by means of traditional techniques for painting and coating, including brushing, spraying, rolling, etc. , and also including centrif ugation . The mass may contain additional bodies of the types mentioned in the above-mentioned patent appHcations such as fibers, plates, or compact particles , and additives such as accelerators or retarders .

O

Another method is to premix part of the DSP material and place it according to the above technique in a situation where a sub-layer and/or additional additives and/or additional bodies are pre-placed (typicaUy reinforcement in the form of nets, webs, yarns or ropes of fibers , including steel fibers, mineral fibers , glass fibers , asbestos fibers , high temperature fibers, carbon fibers, and organic fibers, including plastic fibers, which fibers or nets or webs thereof may contain additives such as accelerators) prior to the appHcation of the DSP material. Where additives and/or ad- ditional bodies are placed later (typicaHy compact particles, nets , fibers, etc. ,) by means of the above-mentioned processes, or where additional bodies are placed simultaneously with the mass or part of the mass . A particularly suitable process is a modified so-caHed dry-spraying technique where coarse, dry particles (e .g. fine sand, sand and/or stone and/or fibers) are conveyed to the surface and impacted against the surface (typicaUy by pneumatic means) with simultaneous impact of very flowable DSP paste (e . g. superplasticized cement paste with ultra fine coUoid siHca particles (eUer siHca dust) with a water/powder ratio of 0.20 -0.30) . This is in many respects a very interesting process because it overcomes two aspects which have hitherto rendered the use of DSP materials in spraying difficult:

1) The technique often reported to give the best coating of sprayed concrete is based on simultaneously impacting dry material (e . g. cement, sand or stone) and water. With DSPmaterials , this technique would be problematic, because the surface- active agent (dispersing agent) would not have enough time to exert its function during the compaction process during the ultra short time of impact.

By use of a superfluidized premixed DSP paste as replacement of water in this technique, this problem is overcome.

2) The elimination of locking surface forces in the DSP materials normaUy prevents formation of thicker layers of coating which are self-carrying against the action of gravity immediately subsequent to appHcation . By use of thin DSP paste combined with relatively coarser particles (particles C or D) (particle size at least one

^ J RE ^

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90

order of magnitude larger than the maximum size of the particles B , but not too large as this would result in ? too smaH -stabilizin Hquid meniscus as explained in the foHowing) , it is possible to obtain a capHlary-bound particle system where the DSP paste is the capiHary Hquid. The requirements are:

a) the amount of DSP Hquid should be sHghtly below the amount necessary to completely saturate the coarse particle system,

b) the fluidity and the particle size of the DSP Hquid slurry sho permit formation of the menisci responsible for the stabiHty,

c) the gas/Hquid interphase tension responsible for the above¬ mentioned stabiHty should be as high as possible. (With respect t the latter, the dispersing agent "Mighty" (the chemical compositio of which is stated in the above-mentioned patent appHcations) is exceHent as it only acts as dispersing agent with almost nH effec on the water /gas interphase tension) , and,

d) the smaHest particle of the coarse particles should not be too large as the stabilizing force, as a first approximation, is inverse proportional to the size of those particles .

Another very interesting aspect is the use of sedimentation technique to obtain an extremely dense packing of particles in th coating (additional bodies C or D in an A - B -matrix or of partic B in an A-slurry) . This can be obtained by sedimentation in a strongly fluidized DSP paste or ultra fine particle suspension (th fluidization being preferably enhanced by high frequency vibratio preferably in the ultrasonic range) .

The particles to be sedimented should preferably be large compar to the particles B of the DSP materials (at least one order of magnitude larger) . The sedimentation is strongly improved by a low concentration of particles being fed, as this means that there is a low rate of feeding of particles , permitting the individual particle freely to orient on the bottom layer constituted by previously added particles so that they are not impeded by settli

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neighbour particles (vide Fig. 48) . This is of special importance with particles or bodies that are not of a compact shape (fibers and plates) , but even for compact shaped particles , it is of signifi¬ cance. The sedimentation may be forced by gravity or forces of inertia, typicaHy by a centrifugation technique.

Another important technique is to place fluid DSP materials together with nets , webs or continuous fibers by filament winding (in such case, the technique is often improved when the fiber material has been prewetted in DSP material) or other types of arrangement of the DSP materials together with the fibers or webs .

Another very interesting technique is to prepare the particle/fiber part as a dry fiber- or net-bonded mass containing the compact particles (typicaHy particles B , e.g. cement, and particles A, e .g. ultra fine siHca dust) , and optionaUy additives as dry powder state dispersing agents (typicaUy "Mighty" as a dry powder) . When placed in position on the surface to be coated, the dry mass is infiltrated with Hquid (typicaHy water) , possibly as a solution of additives, (typicaHy dispersing agent and/or accelerating agents) .

The dense packing of the wetted material is preferably ensured by mechanical action simultaneously with the infUtration, that is mechanical pressing and pressing assisted by vibration or centrifugation. These techniques require extremely good wetting properties of the sohd to be infiltrated. It may be necessary to pretreat the sohd or part of the sohd with surface active agents which improve their wetting properties .

Another interesting process is to place the coating or part of the coating as a prefabricated, non-soHdified fabric, typicaHy fiber-borne

(the fibers being in the form of nets or webs , etc . ) on the sur¬ face to be covered or on a preformed surface layer by winding, pressing or rolling. The fabric may be produced by extrusion, filament winding, or any technique of the type used, e . g. , in paper making and asbestos cement production . The fabric may be prevented from premature soHdification by any means delaying soHdification, e .g. by freezing, which permits prefab rication long time before use and also permits the transportation over long

distances in frozen condition . Immediately before use, the soHdi¬ fication process of the fabric may be activated (by thawing or by chemical or radioactive means or by other heat treatments , e .g. the exothermic polymerisation of an incorporated monomer or ohgomer) .

A special product of this type may be prefabricated from fiber borne DSP materials made, e.g. , from cement, siHca and "Mighty" etc. , and a special appHcation thereof is as a coating for gas pipes of steel and other steel surfaces to secure a high corrosion re¬ sistance .

Another interesting technique is to prefabricate the coating ac¬ cording to the principles mentioned before and soHdify the coating before connection to the surface to be covered. The connection between the coating and the substrate can be secured in several ways :

1. By fabricating the article to be covered against the coating, i.e. typicaHy by using the coating as a permanent mold. This may typicaHy be done when protecting an article of concrete, gypsum, and other materials cast from wet mass at room temperature . But this method may also be appHed to other materials cast at higher temperatures , e. g. , plastic, metals , glasses, etc. In this case, heat stabiHty of the coating may be required.

2. By "glueing" the coating to the surface, e . g. by the use of a "glue" based on a DSP material. The coating may fit more or less exactly to the surface (the shape of the surface of the article being almost identical to the shape of the surface of the coating facing towards the article) . The coating may be flexible in bending, permitting a large capacity of adaptability in shape. This type of coating may typicaHy be fiber borne or fiber reinforced . The fa¬ bricated coatings may typicaHy be made in flat shapes or in roHs, or they may have a structured surface or shape prepared by ex¬ trusion, pressing or rolling to obtain a surface pattern or a shape which makes them immediately appHcable on the surface to be coated Such shape may serve several purposes, one being the desire to

retain the shape in question as a surface of the final articles , another being to secure a good adhesion between the coating and the article to be coated, and a third purpose may be to secure that the coating is self-bearing during the manipulation operations . In many cases some micro-cracking may be tolerated. This permits the use of thin fiber borne particle cement paste DSP film permit¬ ting a high degree of bending (large changes in curvature) . For this purpose, it is preferred to use

1) thin coatings ,

2) large amount of ultra fine fibers .

With regard to this, the special DSP structure permits fabrication of very thin films (typicaHy 400 - 20 μ) with ultra fine fibers (typicaHy 0.1 - 10 μ) very weU fixed in the material, such film having a high mechanical quaHty (with respect to hardness , density and corrosive resistance) . By using less curvature in bending, the principle can also be used for thicker coatings (in the centimeter range) where new development as prefabricated coating on roads , roofs, floors , etc. may be mentioned. This permits prefabrication of e. g. roH-up top layers for road, roofs or floor which are rooled out in situ and "glued" to the substrate, e. g. by means of fluid DSP materials such as DSP paste.

The prefabricated coating may have various shapes , i. e . flat or corrugated, and may be provided with desired patterns or incor¬ porated pigments . Thus , for example, if a road surface layer is made as a prefabricated DSP fiber-borne material, the necessary edge markings , pedestrian passing, etc. may be incorporated in the prefabricated DSP surface . The fixation of the coating may be obtained by glueing, i. e. by means of DSP materials , and/or by mechanical fixation (screws or naHs etc. ) . This technique is par¬ ticularly useful where it is desired to

1) obtain high quaHty coating which may only or best be fabricated under specific conditions (temperature, chemical environment, me¬ chanical fabrication techniques , etc. ) ,

2) place the coating in a condition where it is undesirable to use ordinary technique for DSP material coatings , i. e. underwater coating (off-shore constructions, harbour constructions , ships , etc. ) , with e.g. cement- sHica-Mighty based DSP materials .

In general, a DSP-coated article can be produced either by finish¬ ing the uncoated article and then placing the coating material in a non-soHdified form on the surface where it soHdifies, or the reverse procedure where the finished coating is connected or bound to the material of the article to be coated in a non-soHdified form whereafter the material is sohdified, or any intermediate process combing semi-manufactures of either coatings or part of coatings or semi-manufactures of either the articles or part of the articles .

When DSP materials are prepared as fiber-borne prefabricated sheets or roHs, they may be appHed as a single layer on the articles to be coated, or several sheets or layers may be super¬ imposed, where the binding principle between the single layers may be either a binding" comprising DSP materials or a binding of any other suitable type. For example, a refractory coating may be produced at high temperatures for later appHcation as a prefa¬ bricated sheet. An optimum hardening of the DSP film and the avoidance of undesired drying out of any zones in the DSP film may be obtained by working under controUed conditions in an industrial plant preparing a prefabricated DSP coating. As indica¬ ted above, it is also possible, in an industrial plant, to arrange fibers and additional bodies in an organized manner, including incorporating webs or fibers as carrier layer or merely as incor¬ porated reinforcement.

By incorporating suitable particles or bodies in paints or surface coatings incorporating DSP materials , the desired electrical, optical, magnetic and other properties may be imparted to the DSP materials . When the DSP materials are made as prefabricated coatings as de- scribed above, the coatings may be appHed on the surfaces to be coated by suitable forces . In certain cases, it may be advantageous to utilize electrical or magnetic forces to place a prefabricated DSP coating on the desired location of a surface. Another possibility is

to supply the DSP material with an adhesive back and place the DSP material in much the same manner as self-adhesive tiles , laminates , or tapes (depending on the thickness) are placed. When coatings of DSP materials , either prefabricated or generated in situ, are to show extreme density, they may be impregnated, e.g. with polymers, etc. , in the same manner as disclosed in the above¬ mentioned patent appHcations .

To achieve stabiHty of a DSP material stored in containers or immediately after appHcation, the effect of gravity on the DSP material should preferably be minimized to avoid undue removal of the DSP material from the appHcation site by gravity, or undue particle settling in the DSP material stored in a container. To obtain this , it is desirable to impart thixotropic properties to the DSP mass . This can be done by modifying the particle system itself, typicaHy by use of ultra fine particles A or by introducing additives to the vehicle Hquid, e.g. organic fine elements (large molecules, fine fibers, typicaUy on a ceHulose base (MethoceU)) or inorganic particles, typicaHy smaHer than the particles A . For example, a thixotropic effect may be obtained by introducing 1 - 2 per cent by weight of ultra fine coUoid siHca (typicaHy AerosH 200 or AerosH 380 with specific surface of approximately 200,000 or

2 380,000 m /kg) in an easHy flowable DSP paste based on Portland

2 cement, 20 per cent of siHca dust (specific surface 25, 000 m /kg) , Mighty and water with a water /powder ratio in the range of 0, 25 -

0,30 by weight. For high shear fabrication techniques , a good dispersion of the ultra fine particles is strongly dependent on applying high shear stress on the Hquid vehicle. By use of low viscosity Hquid vehicles this may require an unreaHstic or impracti-

(• _ -ι cable high rate of shear (10 sec. ) . By the use of thickeners

(typicaHy components with large organic molecules , ultra fine fibers or ultra fine particles) , the viscosity of the vehicle Hquid may be inereased considerably. With reference to the example above, an increase in viscosity of a water vehicle from 0.01 cp to 1000 cp by use of a thickener would lower the requirement to the rate of shear to create the required stress from 10 sec. ^" to 10 sec. .

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LARGE STRUCTURES

There has always been a desire to buHd large structures - domes, bridges, towers - for prestige or to serve special practical pur- poses such as haHs for large industries , hangars, sports haUs, towers for TV communication etc. , and, perhaps most important, large subwater structures to support oH- drilling (off-shore) (the hitherto largest in the world contains 600,000 tons of concrete) .

The maximum sizes of many of these structures are Hmited by the weight of the structure itself. This is due to the fact that an in¬ crease in size of a structure - on the assumption that the shape is unchanged - increases the weight of the structure proportionate to

3 the length dimension in third power (F « pgL , wherein p is the density in kg/m 3 , L is a characteristic * length in meters , g is the

2 acceleration due to gravity in m/s , and F is the gravitational effect on the structure), whHe the internal resistance of the struc¬ ture (which is proportionate to a section area) only increases with

2 the length dimension in second power (F « σL , where F is the internal resistance of the structure, and σ is the ultimate stress of the material in Pa) . The maximum size of the structure is deter¬ mined by an equilibrium between the forces in a situation where the load is equal to the ultimate load of the structure (F = F ) , g r" which is seen to be conditioned on a force ratio equal to 1 or

^r- = constant

L = constant x (- ) x -

P g The main parameter responsible for the limitation of size (L) is the stress/density-ratio (σ/p) of the construction material (assuming optimal shape of the structure is used) . The larger the stress/ density-ratio of the construction material, the larger the possible size of the structure, (L) being directly proportional to σ/p . Most large self-supporting structures , typicaHy with sizes of several hundred meters, are made of steel reinforced concrete or struc¬ tural steel or a combination of these materials (the concrete t ^r - picaUy forming the base structure) due to the relatively high

stress/density-ratios of such materials compared to any other materials which might be accepted from practical and economical points of view, i. e . bricks , timber, etc. ) . Fiber-reinforced plastics , boron-fiber-metal composites and other expensive materials having higher stress-density ratio are not reaHy candidates for such large structures .

Stress/density-ratios for concrete and structural steel are typicaHy in the range of 12,000 - 24, 000 (m/s) ² and 40, 000 - 50,000 (m/s) ² , respectively referring to compressive strength of concrete cylinders of 10 cm in diameter, 20 cm in height concrete cylinders (and yield stress of the steel) .

The Portland cement DSP materials typicaHy used as concrete or mortars , have strongly improved stress/density-ratios compared with concrete (typicaHy 2 - 4 times higher than for traditional high strength concrete) . The figures , stress/density ratios of these DSP materials, even exceed those of high quaHty structural steel.

Thus , DSP materials made with Portland cement + siHca dust and natural aggregates (compressive strength ^ 150 MPa, density 2600

3 kg/m ) have been found to have a stress/density-ratio of 57,000

2 (m/s) (14% higher than the above-mentioned high quaHty struc- tural steel) , and ultra strong DSP materials based on Portland cement and silica dust and sand of refractory grade bauxite (com- pressive strength ~ 270 MPa and density 2850 kg/m ) have bee snn found to have a stress/density-ratio in excess of 90, 000 (m/s) 2' which is almost twice as high as that of structural steel.

(An exact evaluation should be based on steel-reinforced DSP materials , which would typicaHy decrease the stress/density-ratio a few per cent due to a shght increase in density. )

This opens up the possibilities of making structures of hitherto unknown large sizes , typicaHy 2 - 5 times larger than the largest

- O EAlT

possible concrete structures, and 1.2 - 2 times larger than the largest possible steel structures .

Large structures designed basicaUy to carry their own weight are often shaped to transfer their load in compression, i. e . towers and most arcs .

Towers .

As a curiosum, an Illustrative way of visualizing the stress/den¬ sity-ratio is the height to which a vertical prismatic tower could be built before it coHapses under its own weight. Ordinary quaHty concrete, high quaHty structural steel and DSP materials could be buHt to heights of 2400 ^' meters for concrete, 5200 meters for high quaHty steel, and 5900 meters and 10070 meters, respectively for

DSP (the last value exceeding 10 kHometers refers to a bauxite- based cement-sHica (20 cm x 10 cm diameter specimen having a compressive strength of 282.7 MPa) .

The designer of ultra high structures would choose a more suitable shape than the prismatic shape, typicaHy with an upwardly de¬ creasing sectional area (thickness) .

This permits stabiHty of towers far taHer than the above-mentioned prismatic towers, even when applying a reasonable factor of safety, say 2.5.

On the idealized assumption of a tower on a rigid base in a uni¬ form gravity field an optimal shape exists (sohd of revolution with upwardly exponentiaHy decreasing cross-section) which, from a purely mathematical point of view should be used for buHding an infinitely taH tower with any part of the entire volume being sub¬ jected to the same compressive stress .

Reference is made to Fig. 69 with appertaining explanation below.

The distance L is the distance upwards before the thickness of the tower has decreased to a specific fraction (for reasons ex¬ plained in connection with Fig. 69, the value 1/e = 0.36S has been

chosen) . This is a measure of the practical possibUities of buHding high towers of finite height with weH-defined thickness in the upper part. The characteristic length L is actually twice the stress/density-ratio (-) divided by the acceleration due to gravity

(g) .

Thus, for example, a four time increase in stress/density-ratio increases the critical length by a factor of 4, and thus increases the height at which the thickness is , e. g. , 1/20 of the thickness at the bottom, by a factor of 4. This means again that the stress/- density-ratio is a main material parameter limiting the size of the structures .

The properties and stress/density ratios of the materials relevant to the present aspect appear from the foHowing table:

Table A

Compressive Density Stress/density- strength or ratio ₉ yield stress kg/m ³ ( /sr MPa

Ordinary concrete 40 2400 16, 700

High quaHty concrete 60 2500 24,000

Ordinary

DSP

150 2600 57, 700

Ultra strong

DSP

270 2850 94,740

Structural Steel 400 7850 51,000 "Dorman 30"

-

* The highest values of a single 20 cm x 10 cm diameter cylinder with refractory bauxite bodies C was 282.7 MPa - 2861 kg/m -

2 98812 (m/s) which corresponds to an ultimate height of a "pris¬ matic tower" in excess of 10 km.

The differences in the maximum height of towers (with a top dia¬ meter of 200 meters and calculated in accordance with the above assumption) corresponding to the differences in the stress/density ratios clearly appear from Fig. 69.

Apart from the high increase in maximum height when using DSP- material instead of concrete, calculations show that, e. g. for towers of a height of 5.8 km the volume of material, calculated according to the above assumption, would be 1/15 and 1/30 of the necessary volume of ordinary concrete if ordinary DSP and ultra strong DSP, respectively, were used.

Compression arches .

(Bridges, Domes etc. )

From principles of equHibrium , it can be shown that the com- pressive stresses in an arch (single-curved ) loaded with its own weight is approximately σ = R ^" pg wherein R is the radius of curvature, which means that

R + SL

Pg This means that the maximum radius of curvature R is equal to the ultimate value of the stress/density-ratio of the material divided by acceleration due to gravity.

Using a factor of safety of 2.5 and the same materials as in Table A, the maximum size of self-supporting compression arches (with an aperture angle V = 30°) wiH be as shown in the foHowing table B

* For double-curved shells with main curvature radii Ra and RT,r , R is to be replaced with R* defined by: λ = λ ₊ λ

R R a *b

170

101

Self-supporting compression arc. Factor of safety 2.5.

Table B σ/p ₂ R L Rise

(m/s) m m m

High quaHty concrete 24,000 978 506 33

Structural steel 51,000 2079 1076 71

Normal DSP 57,700 2352 1217 80

Ultra strong DSP 94,740 3862 1999 132

Spatial constructions with double-curved sheHs facings may also advantageously be analyzed in terms of radius of curvature where the maximum resulting radius of curvature R* equals - .

Beam constructions may often advantageously be considered in the Hght of arch effect, the beam being considered as a compression arch with excess weight. With reference to Fig. 75 the use of ordinary beam calculation presuming Hnear elastic behaviour results in balance moment between external load (gravity) and internal resistance

4 rr T

1 = - - , (Section type I)

3 pg -

1 = 4 — ₉ (Section type II)

For smaH values of height/length ratio H/L, this corresponds to

T 2 radius of curvature for stress lines (R ~ _HTT )

R ^~ =-§ jj (Section type I) R - \ ?- (Section type II)

*-• pg

-^ JRE c

102

It is assumed that the concrete and DSP elements are reinforced that tension is carried by the reinforcement and compression by the concrete or DSP.

A complete utHization of the ultra strong DSP material (compressi strength 270 MPa) in bending members requires high concentratio of very strong reinforcement in the tensHe zone, i. e. , high ^" strength wire with tensHe strength in the range of 2000 MPa in a concentration of about 10% by volume of the tensHe zone.

As previously mentioned and Hlustrated in Figs . 69, 70, 72 and 73, DSP is extremely suitable for very large constructions where weight of the structure is the dominating load due to the fact tha the stress/density-ratio of the material is much larger than is the case with concrete and even considerably larger than for quaHty steel for structural purposes . This can also be utilized to make much more slender structures, as Hlustrated in Figs . 71 and 74.

Table C

Minimum thickness for homogeneous, self- supporting, horisontal beams (with rectangular cross section) or plates simply supported along two opposite edges in the distances L = 30, 60 and 120 met respectively. Safety coefficient 2.5.

Material Thickness of beam or plate (cm) L = 30 L = 60 L = 120

Ordinary concrete 100 400 1600

High quaHty concrete 70 280 1120

Structural steel 33 132 528

DSP-N 29 116 464

DSP-S 18 72 288

- -

Another very interesting use of DSP to replace concrete is in slender structures designed to resist wind load or load from water streaming relative to the structure .

According to hydrodynamics, the load acting on the structure, say a cylindrical pole, is proportional to the area of the pole met by the fluid, i.e . , the moment tending to break the pole in bending is

2 proportional to the diameter m first power: M « p ' d ' L '

However, the internal resistance against bending of the pole is

3 proportional to the diameter in third power: M « σ .

The condition of equUibrium (M = M ) thus- requires

L ^} σ

From this it wiH be seen that DSP makes it possible to decrease the structure diameter considerably which results in much more slim structures or elements .

Thus, a typical 4 times increase in strength by use of DSP having a compressive strength of 160 MPa instead of concrete having a strength of 40 MPa results in

reduction of the diameter to 1/2, reduction of area and volume to 1/4, and an unchanged amount of steel reinforcement.

This is because a decrease in the diameter to 1/2, the load is correspondingly decreased to 1/2, which is balanced by an eight-fold decrease in resistance moment and a four times increase in strength.

The amount of steel reinforcement is substantiaHy unchanged.

This can be expressed more generaUy in the foHowing way:

1) An increase in strength from σ to fxσ results in

2) a reduction in structure diameter from d to r~ ,

3) a reduction in volume from V to γ, and

4) a reduction in weight from W to W{p _Q /p} , where the last term is the density ratio (normaUy being close to 1 in case of concrete and DSP), whHe the amount of reinforcement is unchanged.

The large bending member structures rendered possible through the DSP matrices, hence, considerably surpass known structural material with respect to obtainable size of the members . Hence, one aspect of the invention comprises a substantiaHy horizontaHy arranged structural member having a rectilinear or convex upper surface and having such a shape and size that a radius of an arc of a circle extending in a vertical section of the member and touching said upper surface and intersecting with the lower surface of said structural member at positions located between two adjacent supports of the structural member is at least 1000 meters .

It should be noted that a member having the above characteristics could not be prepared from high quaHty concrete, but may easHy be prepared from normal DSP. Structural steel could, however, also be used for such a member.

According to an embodiment of this aspect, the radius is at least 2100 meters, which exceeds what could be made in structural steel, but which could stiH be made in normal DSP. According to pre¬ ferred embodiments of this aspect, the radius is at least 3000 meters and at least 4000 meters, respectively, both of which are structures which can be made in DSP with ultra strong bodies C such as appears from table B .

When the structural member, however, is prismatic, it wiH be loaded with its own weight to a higher extent, cf . Fig. 75, and in such a case, the above-mentioned values should be replaced with

500, 1050, 1500, and 2000 meters, respectively . If the structural member has a rectangular cross- section, the conditions are, again, less favourable because of a higher load of the weight of the struc¬ ture itself, and the above-mentioned values should be replaced with 136, 350, 500, and 667 meters , respectively . However, in aU cases, the same relation between the DSP material and ordinary high quaHty concrete and structural steel as explained above wiH apply.

HIGH QUALITY FOAM

A particularly interesting appHcation of DSP-materials is the pro¬ duction of high quaHty sohd foam typicaHy with low density, con- troUed pore size and pore shape, with strong thin continuous waUs between the pores . The high quaHty foam has very special pos¬ sibUities of producing foam with micro pores , typicaHy below 100 μm and even below 1 μm.

By traditional foaming technique with incorporation of air bubbles by mechanical or chemical means it is possible to make Hghtweight foam, or more specificaHy, foams with a low concentration of sohd substances .

However, the known technique suffers from certain disadvantages :

1) It is difficult to form Hghtweight foam with strong waUs, be¬ cause the foaming technique requires an easHy flowable Hquid which in many cases is not compatible with demands for high strength of the soHdified material (typicaHy for materials where the fluid is a slurry, containing the particles responsible for the later structure such as cement materials and ceramic materials) .

2) It is difficult to control the geometry of the pore system, both with regard to formation of the desired pore size and stabilisation of the pore system.

- EA ?-

3) It is difficult and often impossible to produce pores having shapes which differ considerably from the traditional shapes cha¬ racteristic of surface-force-controHed foams .

It is also known to produce foam by casting of a fluid with Hght¬ weight particles (e. g. polysterol particles) . This secures the de¬ sired pore size, but this technique makes it generaHy difficult to obtain

1) high quaHty of the sohd walls (vide item 1 above) and

2) a very low specific weight (low soHd concentration) , as the space between non-deformed discrete particles is normaUy large, typicaHy above 30 - 40% (vide the geometry when packing of uni- sized spheres) .

Due to the combination of easy flow and high mechanical strength, rigidity and durabHity, the use of DSP-materials wiH strongly increase the quaHty of foams prepared according to the two tradi¬ tional methods mentioned above by strongly increasing the strength of the waUs and making it possible to achieve higher content of

Hghtweight particles by the use of gap-grading (mixture of large and smaH particles) or other geometrical means made operative with the easHy flowable DSP-paste.

It is known to overcome the difficulties in producing Hghtweight foam based on Hghtweight particles by deforming the particles prior to casting, for example by prearranging the polystyrol spheres in a box which is compressed about 30%, and then infiltrate the remaining space with the material (fluid gypsum) by means of vacuum.

Thus , a Hghtweight material is obtained, but the "foam structure" has some severe drawbacks, primarily that the contact between the compressed particles prevents formation of the continuous walls which characterize a good foam .

Besides , the technique is difficult, especiaUy in the case of finer foam structures where infUtration is difficult and where the infil-

tration Hquid cannot contain particles or fibers having sizes above 1/10 - 1/20 of the size of the pore in order to obtain a reasonable infUtration.

This is fatal to the formation of ultra fine foam (with a pore size of about 10 μm - 1000 μm) using particles based on waH materials with maximum particle size of about 0.5 μm to 100 μ ., typicaUy for particles B of the DSP-material.

The present invention completely overcomes these difficulties and permits fabrication _. of high quaHty foam with a high volume concen¬ tration of voids, strong waUs between the voids, typicaHy with DSP-paste, possibly fiber-reinforced, and foam with weH defined waH structure, especiaHy high quaHty ultra fine pore-based foam.

The foam shaping is based on introducing Hghtweight bodies (par¬ ticles , fibers etc . ) to a fluid DSP-paste (hereby creating the Hght¬ weight structure) or other deformable bodies which are removed after hardening and which leave the material with the desired pore space, the high void content obtained mainly by deformation (for example compression) of the introduced pore- creating bodies .

According to one embodiment, the foHowing procedures are foHowed: The fluid DSP-paste and compressible Hghtweight particles (e.g. polystyrene spheres of 1 mm) are thoroughly mixed and the material is 1) placed in a closed container. 2) Pressure is appHed to the fluid. 3) The compressed Hghtweight particles are aUowed to coUect at the top or at the inner surface during centrifugal casting. 4) The piston is moved upwards, aHowing surplus fluid to escape whHe the fluid pressure is maintained. 5) The force on the piston is slowly released and the piston is aUowed to move outwards avoiding any mass transfer to or from the enclosure. (IHustrated in_Fig. 57 - 61) .

Comments :

1. It might be desirable to simply compress the particles in posi¬ tion 1) under draining conditions which permits surplus Hquid to

- OTEA ^* ^

-

108

escape. With smaH particles, large thickness in direction of Hquid drainage and a desire of obtaining large deformation of the par¬ ticles, the fluid drainage would be blocked or at least strongly delayed. This fundamentaUy simple solution seems highly unreaHst in connection with high quaHty DSP-paste-based fine foam.

2/3. By applying pressure, the volume of the particles is decreas permitting a denser packing. The pressure- determined flow may b assisted by mechanical vibration resulting in increased fluidity of the paste and denser particle arrangement. Centrifugal technique in order to increase the rate of particle flow may be appHed.

4. The piston has to be moved upwards to the position which de¬ termines the final amount of fluid to be contained in the foam artic This movement must take place whHe maintaining the fluid pressur to ensure the compressed state of the deformable particles .

5. The release of the piston force avoiding any mass transfer between the enclosure and the environments creates a foam con- taining continuous "waH material" with completely discrete voids and a pore volume determined by the appHed stress levels and the compressibility of the particles .

It is to be mentioned that the particles are in mutual compression whHe the fluid is under tension just after the release .

Release of the force does not mean change of the force to zero, but a reduction of the compressive force in general which results in a somehow smaHer compression.

One of the major advantages of the method is that there is no in¬ ternal mass transport (except from local arrangement around the particles) during the actual foaming process .

The general principle of the foam shaping process is

1) to have the void-forming material in a compressed state (e.g. polystyrene spheres) together with aU the fluid material which later is to form the soHd waUs in an enclosure, and

2) to release the external forces on the outer limits of the en¬ closure which permits expansion of the voids without mass transfer between enclosure and surroundings . ^~

The void forming material may be Hghtweight soHd compressable material (e. g. polystyrene) , hoHow compressible material (e. g. hoHow thin-waUed plastic spheres) , gas bubbles , typicaHy stabilized by foaming agents (or material as aluminum powder in a water-based slurry which develops gas) .

The voids may be of arbitrary shape obtained by the use of void- forming particles of arbitrary shape.

Special products may be produced with rod-shaped pores arranged paraUel, i.e . a kind of honeycomb structure . The void expansion may be obtained by introducing fluid (gas or Hquid) into hoHow void-forming bodies , i. e. blowing gas into hoUow micro- tubes of plastic or rubber and expanding a fiber of a material which ex¬ pands in water. The water is introduced by capHlary action which technique requires through- going pores .

The void-forming material may be removed by melting, evaporation, chemical solution or it may be mechanicaUy drawn out, typicaUy in a foam with paraUel prismatic pores , i. e . using a rubber band as a void-forming material.

Variations .

Introduction of the void-forming compressed particles to the Hquid as individual single particles in order to obtain an extreme dense Hghtweight particle arrangement prior to the expansion .

This technique makes it possible to buHd-up a very sophisticated internal pore structure combining many types of pores in desired arrangements .

(This technique of forming high quaHty foam is beHeved to be novel, also without use of the pressure-pressure release technique to obtain the very hight void content. )

Another method which is especiaHy suitable in order to produce paraUel ahgned pores is to wind the pore shaping material, i. e. a

^• rubber string, up in a slurry of DSP-material, thus achieving the dense packing by deforming the rubber string during the winding process, either due. to cross deformations (flattened rubber band) or by released tension.

COMPRESSION SHAPING OF DSP

A speciaHy promising production for producing articles of DSP is compression shaping from DSP materials having a plastic to stiff- plastic consistency.

This is a fast process which requires considerably less mold material than ordinary casting, and which permits the preparation of products of a considerably higher quaHty than is obtainable by ordinary casting, considering that the water/powder ratio is con¬ siderably lower in compression shaping (typicaHy 0.08 to 0.13 versus 0.20 in ordinary casting of cement/siHca paste-based articles) , and which permits incorporation of more fibers and finer fibers in the compression-shaped masses (thus, e.g. , the com¬ pression shaping of plastic cement/siHca paste is performed using up to 6 per cent by volume of glass fibers of diameter 5μm and length 12 mm) .

Prior to the compression shaping, the semi-finished product is formed which subsequent to the compression becomes the desired article. The semi-finished product is formed by mixing processes and various forms of pre-treatments (e. g. , extrusion or rolling) to

ensure a desired fiber orientation and a desired starting shape of the semi-finished product.

The semi-finished product is placed in a press , a rolling mHl or the like the faces of which facing towards the product ensures that the compressed articles obtain the desired shape. Examples are shown in Figs. 24 to 30.

By moving one or several parts of the compression tool, the material is pressed into the cavity, thus forming the desired article having the desired shape.

Upon removal from the compression faces, the shaped article may be withdrawn from the press to a lesser or greater extent sup- ported by mechanicaUy stable molds, the requirements to the stabilizing molds being dependent upon the mechanical stabiHty of the compressed material, the geometry of the article (size and shape) , external influences subsequent to the compression (gravity, vibrations, etc. ) and the requirements concerning the dimension and shape tolerances of the article.

Semi- Finished Product.

In the present context, the term "semi-finished product" de¬ signates the bodies which, on compression are converted into the compression-shaped articles .

The semi-finished articles may be formed from the above- described components (particles, fibers , other components , Hquids , etc . ) and may, likewise, be shaped in one of the above- described processes for shaping the finished article (extrusion, rolling, vibropressing, spraying, etc. ) , or by compression shaping (when the production is performed by successive compression shaping operations) .

The semi-finished products may be formed from various partial components which, in the compression operation, are shaped to form a unitary product. Thus , e. g. , panel-shaped articles having

-g J E

specific fiber arrangements may be formed by placing layers of thin extruded panels (with the fibers substantiaHy oriented in the direction of the extrusion) in suitable and desired orientation relative to each other, such as Hlustrated in Fig. 25, and desired articles to be incorporated, such as electrical resistance units, tubes, cables, sockets, reinforcements etc. , or various other parts (steel panels, wood bodies, etc. ) may be cast into the resulting article in the compression shaping, such as Hlustrated in Figs. 24 - 27.

Compression

As mentioned above, the compression is performed by moving one or several parts of the compression tool relative to the material to be shaped, and thus pressing the material into the desired shape.

Often, the shaping cavity is closed aU over, and the material is made to fiH aU of this room by being pressed against non-resHient mold sides . This is a compaction process .

In other cases, the compression is performed in cavities which are not completely closed on aU sides . An important example of this is the compression process termed extrusion where material is pressed out of an orifice having a specified cross section, thus resulting in an article having said cross section, or by a stamping which is often a local compression shaping. A speciaUy interesting technique is rolling with flexible roUers . The rolling with flexible roHers , invented by the present inventor, is described in greater detaH in a Danish patent appHcation filed on May 1, 1981, in the name of

Aktieselskaber Aalborg Portland- Cement-Fabrik and entitled "Valse og fremgangsmade til. valsning af et deformerbart materiale ("RoUer and method for rolling a deformable material") .

As previously mentioned, there wiH normaUy not be any pressing out of Hquid from the blank to the surroundings, which is one of the substantial advantages of the DSP casting mass .

However, using drained compression, it becomes possible to con¬ struct a new type of materials consisting of coarse components (large in comparison with the particles B) arranged in dense pack¬ ing corresponding to what may be obtained with the components in question in a compression process (possibly vibropressing) glued together by means a high quaHty DSP paste.

The specimen consisting of the coarse components is compressed in one of the foHowing manners :

1) With a surplus of Hquid paste (e.g. , cement-sUica DSP paste having a water /powder ratio of 0.20) whichs is pressed out from the specimen, using suitable filter or draining means arranged in the press , (vide Figs . 15, 16 and 17) .

2) with less than the final proportion of Hquid paste - possibly with no Hquid paste at aU, the missing Hquid paste being added by compression, capHlary suction, vacuum suction or simUar means in a later process or during the compression,

3) with an amount of Hquid paste corresponding to the proportion thereof in the final product.

In the first-mentioned case, the compression is , such as mentioned above, accompanied by Hquid expulsion. The compression apparatus is adapted to be able to drain the expeHed Hquid without any substantial interference with the compression process .

Using processes of this kind, it becomes possible to produce articles having a good stability immediately after compaction.

Final Treatment.

After the compression shaping, a specimen having a more or less stable shape has been formed. Dependent upon the stabiHty, various degrees of support of the specimen may be utilized:

1) Support at the bottom or other places exclusively to place the specimen in a desired position (the support may, e. g. , be a floor or a shelf)

2) Support along essential parts of the shaped surface to preserve the shape of the specimen produced,

3) Complete support around the fuH surface of the specimen to preserve the shape of the specimen produced.

The specimen and the supporting means may be combined in the press , part of the shaping surface being a mold which, subsequent to the compression, accompanies the specimen as a shape support (the molds may, e.g. , be thin compression-shaped metal bodies) , or which is brought into contact with the specimen in a separate process after the specimen has left the press.

In many cases, the compressed specimen is surface- treated im e- diately after the compression, primarily to prevent drying out in the further processing.

The surface treatment may be performed by appHcation of curing compounds to avoid evaporation, which may, e.g. , be appHed by brushing, smearing, spraying, etc. , or by appHcation of evapora¬ tion-impeding removable film, after the specimen has left the press or in connection with the compression process by transfer from the shaping surfaces of the press .

In many cases, the above-mentioned supports may also be utilized in the appHcation of a surface treatment, or may render a surface treatment superfluous, or the support may constitute the surface treatment (e. g. , a ceramic sheH appHed in the press) .

FinaUy, the compression may be accompanied by processes securing some kind of soHdification of the specimen - in addition to the soHdification resulting from the pressure itself . As examples may be mentioned simultaneous appHcation of heat (by heat transfer

-g f OMPI

from the press or by electro or micro wave heating) or eHciting of polymerisation of a polymerisable component included in the Hquid phase.

According to a particular aspect of the present invention, a cement/water-based DSP composite material may be retarded with respect to its chemical structure formation and/or stabilized with respect to its shape by freezing the DSP composite or the semi¬ finished product. In this manner, the composite material or the semi-finished product can be pre-mixed or pre-shaped, respec¬ tively, and thereafter transported to a desired site of use where the structure-forming process can be aUowed to proceed further by thawing the product, possibly combined with subsequent shaping. This method may be appHed more generaHy to any type of DSP material where the structure formation can be delayed, retarded or stopped by freezing or a simUar process . The DSP material subjected to this process may be pre-shaped in any of the manners described in the present specification.

SHAPING OF DSP IN A HIGH STRESS FIELD .

Shaping of DSP materials may also be performed in a high stress field, typicaUy between 5 and 100 MPa, in special cases, between 100 and 1000 MPa, and in extreme cases between 1000 and 10000

MPa.

The high stress shaping wiH usuaHy be combined with a pre- shaping of the DSP material at lower stress , typicaUy designed to achieve

1) -an approximate shape of the article, and

2) a desired pre- arrangement of particles , fibers , etc. prior to the final high stress shaping.

The high stress shaping may typicaUy be performed to deform or crush the pre-arranged particles (e . g. a press sintering which is

- θR _ O PI

typical for metal particles, or a particle crushing to stHl finer particles which is typical for brittle materials) .

The high stress field shaping may typicaHy be appHed during soH- dification, e.g. by hot or cold pressure sintering, or - typicaHy fo cement products - by structure formation during hydration.

By the high stress field shaping, denser structures are obtained. It is known to shape articles in high stress fields by powder com- paction, pressure sintering, etc. , but in these known methods, it is not easy and in most cases not possible to obtain a desired pre-designed micro structure. Utilizing the structure formation techniques of the present invention in a superplasticized material in a low stress field, the desired particle/fiber arrangement may be pre-designed, whereafter the high stress treatment may be performed on the thus pre-arranged structure.

The high stress fields shaping may be combined with the technique where a fluid inter-particle material is exchanged by multi-stage infUtration, such as described in the section "HIGH RESISTANCE ,

ULTRA STRONG DSP MATERIALS" . The exchange can be performed as an intermediate process after the basic structure-f orrr.in g pro¬ cess and before the high stress treatment or after the high stress treatment .

Articles which are typicaHy made by means of the high stress shaping are, e.g. , machine parts which are to be subjected to high stress , aircraft or spacecraft parts which are to be subjected to extreme mechanical loads , and other articles which- are subject to severe conditions during their use, including highly fiber loaded articles combining extreme resistance and hardness with high tensHe strength and ductility.

An especiaHy interesting technique is to combine the high stress field shaping with various pre-arτangement methods which are described in the section "COMPRESSION SHAPING OF DS?" . The various semi-manufacture production methods described izz that

section can suitably be combined with a post- treatment of the semi- finished article in a high stress field.

EspeciaHy, the high stress field shaping of DSP makes it possible to combine high hardness and abrasion resistance with a high degree of ductHity (obtained by high fiber load) , which are pro¬ perties which it is normaUy very difficult to combine by. means of known art techniques.

This aspect of the invention may be expressed as a process com¬ prising shaping a DSP composite and/or a DSP semi-manufacture in a high stress field, typicaHy a field of 5 - 100 MPa, in special cases 100 -1000 MPa, and in extreme cases 1000 - 10000 MPa. Another aspect related to the first-mentioned aspect is where a DSP material, e.g. a cement-based DSP material, is soHdified at a high stress level, typicaHy at 0 - 5 MPa, for example by soHdifi¬ cation between platen members in a press . In special cases , the soHdification may be performed at higher stress levels, such as 5 - 100 MPa, and in very special cases at stresses between 100 and 1000 MPa or even between 1000 and 10000 MPa.

If desired, the soHdification in a high stress field may be combined with treatment of the DSP composite material prior to shaping by- high shear treatment, for example by passage, optionaHy repeated passage, through narrow nips of multiple roHers, in accordance with the technique described in European Patent AppHcation No. 80301909.0 pubhshed under PubHcation Number 0 021 682.

MULTI-STAGE INJECTION.

According to a particular embodiment of the present invention, DSP materials are used for multi-stage injection into cavities or ducts .

In this context, injection designates a process where matter is completely or partly made to fiH cavities in soHd bodies . In certain cases, the concept injection in the present meaning thereof wiH also be covered by other designations (impregnation, filling etc. ) .

The purpose of injection is partly or totaUy to fiH cavities with a substance which forms a body, "a f lling" , with a specific struc¬ ture and specific characteristics, often subsequent to a soHdifi- cation process .

In accordance with the traditional technique, injection is often performed by pressing a Hquid or an easHy flowable Hquid sus¬ pension into the cavity to be fHled and then aHowing the Hquid or suspension to cure or soHdify, leaving a filling with a structure which is characteristic of the injection mass in soHd form. For example, for injection of cable ducts in post-stressed concrete, fluid cement paste is often used. Thus, the filling wiH be a body of cured cement paste having the characteristics of this material.

In many cases , a filling with improved properties might be desired, for example a cable filling with a material with greater volume stabiHty than cement paste, e.g. mortar or concrete. However, it is difficult to establish a mortar or concrete filling in view of the demand for fine filling. Coarse-grained materials like mortar or concrete cannot penetrate into the not easHy accessible narrow parts of the cavity in- the zones between cable and duct where the cable is positioned close to the duct waH.

According to the present invention, this problem is solved by injection in two or several steps with two or several injection materials, where the first filling mass(es) cover(s) surfaces and fHl(s) up even the fine, not easHy accessible cavities, whHe the

subsequent injection mass(es) do(es) not have the same ability to penetrate or enter into narrow cavities, but may displace the first injection mass from the larger, easHy accessible cavities .

In this way it is contemplated to obtain a high quaHty filling in cable ducts having a length of, e. g. , 20 - 40 meters and a diameter of 5 - 10 cm and containing a cable with a diameter of 2 - 3 cm, with a high volume of larger particles (e.g. having a maximum particle size of 6 - 10 mm) , but with an encasing and filling around the cable of the same high quaHty as in a pure cement paste filling .

The process is. a two- or three- stage injection starting with a cement paste and finishing with concrete (potentiaHy with an in- serted string of mortar), where the subsequent injection mass displaces the part of the previous masses which is present in the easHy accessible areas where the coarser mass may advance, leaving the less accessible areas fiHed with fine material (vide Figs . 42 and 44 - 46) .

Such a process is especiaHy promising with the new DSP materials based on densely packed particles of the size 0.5 - 100 μm with the interstices fHled with homogeneously arranged and optionaHy densely packed ultrafine particles which are one ^' to several orders of magnitude smaHer than the first-mentioned particles , as these materials have a high quaHty and show exceUent flow properties of the casting masses (even when the concentration of coarse sand and stones is high) and great internal coherence. However, the principles stated above apply in general and are not Hmited to the above materials .

The basic problem may be Hlustrated by the simplified structure shown in Fig. 42, wherein a cavity of in a body of sohd substance is fHled with two different materials by injection.

The reason for using two different materials may be the desire of providing the cavity with specific properties (material I may have specific electrical, chemical, mechanical, thermal, optical or other

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properties) placed at desired places (e. g. as protecting "coating" between the main filling mass II and the external soHd body) , or the reason for using two different materials may be process-tech¬ nical considerations, for example when it is not possible (e. g. for geometrical reasons) to make material II fiH area I or when material I aids in the injection of material II (e.g. by changing the condi¬ tions for interface flow (reduction of friction or changing of the interface tension) or inhibits the separation of injection mass II by blocking the transportation of mass into the waH material) .

The process according to the invention comprises first filling out the total cavity (Hlustrated by the total cross section I + II) with the first material component (referred to as material I) , and sub¬ sequently injecting of the second material (material II) displacing part of material I and leaving a filling comprising both of the materials (cf. Fig. 42) .

The displacement of material I takes place through contact forces from material II (often in the form of pressure or shear), prefer- ably also aided by other forces (e.g. gravity) such as by upward injection of a duct with a Hght mass (I) and subsequently injection of a mass (II) with a higher density.

The injection according to the principles of the present invention requires that part of injection mass I originaHy present in area II is displaced therefrom. In principle, this may be performed by

1) pushing the material forward in the injection direction (which wiH be the usual manner)

2) compressing the material in area I (which is, e.g. , possible if material I or a substantial part of material I is in gas phase)

3) transporting the material into or through the sohd material in which the cavity is (e.g. by injection into cavities and ducts in bodies of porous materials) or transporting the material into injection mass II (e.g. by dissolving injection material I and injection material II) or by

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4) using a combination of two or more of the above-mentioned methods .

As mentioned above, the injection may be performed in several steps, some of which primarily ensure the filling up , whereas others may primarily serve as aid in the performance.

Of the greatest immediate interest is the injection of prism-shaped or approximately prism-shaped cavities, which are characterized in that their dimension in the longitudinal direction of the prism sides are large compared with the cross dimensions, in multistep injec¬ tions , wherein the first step(s) ensure(s) a desired filling up of narrow, not easHy accessible areas and areas in the immedite vicinity of the waUs of the cavities, whereas the last injection step ensures the formation of a composite structure in the readily accessible, often larger part of the cavity comprising a matrix with a dense arrangement of larger particles corresponding to a dense particle packing in accordance with geometrical principles of pack¬ ing of particles.

Two important geometrical features must be - considered when filling up a cavity with a particle material of the highest possible concen¬ tration of large particles : the blocking effect and the waH effect.

The blocking effect occurs when areas are present which for geo¬ metrical reasons are not accessible to the larger particles , cf. Figs . 37 and 50. According to the principles of the present inven¬ tion, these areas are fiHed with a finer material, which may, from a particle- geometrical principle point of view, be placed in these areas . ' ^•

The multi-stage aspect of the present invention which, such as mentioned above, is not Hmited to DSP materials but is quite generaHy appHcable to injection materials , may be expressed as a method for filling cavities in sohd bodies with a substance (U) comprising large particles and a substance (V) comprising smaH particles in such a manner that the substance V only occupies the spaces substantiaHy unaccessible to the substance U, by pre-fiHing

of aU parts of the cavity with substance V succeeded by a filling with substance U, the latter substantiaHy replacing substance V from spaces accessible . to substance U.

According to a preferred aspect of this method, substance U is a Portland cement-based material. According to a further preferred embodiment, the substance V is a Portland cement-based material. According to a stHl further embodiment, the substance U is a DSP material, and the substance V is DSP material.

The cavities to be fiHed may be, e.g. , a duct, a channel, or a pipe, or it may be a cavity between surfaces which is fiHed in accordance with the above-mentioned principle of "casting adjacent to or between surfaces" .

The cavities into which the substances are injected may contain additional bodies prior to the injection, such as pre-arranged rein¬ forcement, pre-arranged aggregate, etc. According to an important aspect of this method, the cavity into which the injection is per- formed contains a bar, a wire, or a cable or several bars, wires , or cables .

METHODS FOR PRODUCING DSP MATERIALS USING A LIQUID VEHICLE TO ASSIST THE SHAPING WITH SUBSEQUENT

REPLACEMENT OF THE LIQUID VEHICLE .

The DSP shaping processes are extremely weH suited for the shaping of advanced structures (containing particles, fibers , webs , etc. ) in desired arrangement by a simple technique such as mixing, casting, extrusion, spray-up, brushing, and filament winding, typicaHy performed at room temperature and without the necessity of ^" using compHcated health- con serving measures . This is demon¬ strated in the present appHcation and in International Patent AppH- cation No. PCT/DK79/00047 for many cement/sHica/water systems .

A direct transfer of the DSP technique to the shaping under high temperature, e. g. , to produce metal- or glass-bound DSP materials ,

or under health hazard conditions, e .g. to produce plastic-based DSP materials based on monomer /polymer transition, may introduce enormous compHcations or may even be practicaUy impossible.

An aspect of the present invention permits the production of such materials with fuH retention of the benefits of the DSP shaping processes and with elimination of almost aU of the compHcations anticipated in the production of, e. g. , metal- and glass-bound DSP materials .

This aspect comprises using a Hquid vehicle in the shaping process and replacing the vehicle in a subsequent process .

This makes it possible to choose a Hquid which is especiaHy suitable for shaping the specific particle structure according to the prin¬ ciples of the DSP materials .

The Hquid vehicle may typicaHy be water-based, but also other Hquids may be chosen, e. g. , if water would exert an undesired influence on the particle system, e.g. by dissolution or chemical reaction, or if the other Hquid chosen results in better rheological behaviour than the water-based Hquid.

Also in this aspect of the present appHcation, the shaping may be performed according to any of the shaping principles described in the present specification.

The Hquid vehicle may be removed by evaporation or displacement with another Hquid as explained in greater detaH in the foHowing section "HIGH RESISTANCE, STRONG DSP MATERIALS" . The

Hquid vehicle may to a higher or lesser degree be retained in the final product, e.g. , in order to estabhsh a certain rigidity of an intermediate structure prior to the infUtration with the final mat¬ rix-shaping Hquid. A typical example of this is where the Hquid vehicle is water which reacts with an inorganic binder, e . g. ,

Portland cement, present as part of particles B .

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The infUtration Hquid may, e. g. , be a monomer or mixture of monomers which is polymerizable to form a desired plastics matrix, or it may be water (in a case where water could not be used as the Hquid vehicle), a Hquid metal, sulfur, or glass . The infUtration Hquid should preferably be capable of wetting the surfaces of the particles, which is typicaHy obtained by means of surface-active agents . The infUtration may be aided by evacuation prior to the infUtration, pressure and mechanical vibration, including ultrasonic treatment. For articles where the internal structure is not suffi- ciently rigid per se to resist the forces appHed during the infU¬ tration, it is necessary to apply external stabilizing forces, e. g. , by enclosure between mold parts, during the infUtration process.

The infUtration Hquid Hquid may be chosen in such a manner that it results in desired physical and chemical properties, such as :

1. Mechanical strength and rigidity.

2. DuctiHty.

3. Specific optical properties .

4. Specific thermal properties .

5. Specific electrical properties .

6. Specific chemical properties .

HIGH RESISTANCE, ULTRA STRONG DSP MATERIALS .

The use of densely packed fine fibers or whiskers together with ultrafine particles one or more orders of magniture smaHer than the fiber diameter and placed in the voids between the fibers opens possibUities of making new, ultra high strength materials with strongly increased resistance.

OM

The strongest structural material hitherto known are made by embedding a high volume concentration of ultra-strong and rigid fine fibers or whiskers in a matrix with ductile behaviour, typicaHy a metal such as aluminium, cobalt, or sHver, or an organic material (various types of plastics) . The very fine fibers are whiskers , including whiskers, graphite whiskers , iron whiskers , boron fibers , silicon carbide whiskers , and glass fibers . The fiber volume may be as high as 50 - 60% by volume.

The design is based on the fact that the tensHe strength of fibers increases with decreasing fiber dimension due to increase of the perfection of the fibers (reduced number of internal flaws) . To secure a good load transfer, the fibers are embedded in a matrix with ductile behaviour. Such materials are typicaHy developed to meet the requirements of high performance with high strength/ density ratio and high elastic modulus/density ratio required e. g. , for appHcation in space vehicles .

The above statements apply to the superior properties of these composites under tensHe influence in the direction paraUel to the fibers . When the materials are under compression paraUel to the fibers , the specimen breaks down by fiber buckling and matrix shear. By mechanical action perpendicular to the direction of the fibers, (tension, compression, abrasion) , the specimen breaks down mainly due to matrix shear. Chemical and thermal resistance, including non-flammabiHty , is largely determined by the bulk properties of the matrix material.

In principle, these deficiencies of the above-mentioned types of materials can be diminished, i. e. , their properties can be improved, by strengthening and stiffening the matrix. For the matrix material in bulk (that is, without fibers) , this can be done, e. g. , by incorporation of hard, strong particles , preferably in a high volume concentration .

These principles are, however, not immediately available in con¬ nection with the ultra highly fiber-loaded composites discussed above, as introduction of particles would strongly violate the basic

requirement for densely arranged ultrafine fibers or whiskers (unless the particles are at least one order of magnitude smaHer than the fiber diameter) .

It is known to incorporate ultrafine compact- shaped particles (size range from about 5 μm to about 50 A) into bulk materials of the kinds used as matrix in the fiber composites .

It is, however, not known to perform this in the type of fiber composite in question, which may be due to great difficulties in the production of such combinations . The usual technique based on infiltrating the fiber arrangement with the matrix as a Hquid would not permit incorporation of ultrafine particles by simple suspension of the particles in the Hquid as the geometrical fiber arrangement (typicaHy paraUeUy arranged, densely packed cylindrical fibers) exerts a tremendous infUtration resistance, rejecting even the smaH 50 A particles .

The present invention comprises forming the previously described composite structure with extremely densely packed fine fibers or whiskers in a sohd matrix (typicaUy metal or plastic) in which - as the new aspect - the matrix material is reinforced with ultrafine soHd particles , typicaUy having a particle size of from 5 μm to 50 A, homogeneously and/or densely arranged in the matrix, without violating the basic principle of dense arrangement of the fibers , . and by use of a mechanicaUy simple production process in order to avoid damage of the fibers .

This has been made possible by use of the production technique for DSP materials described in the present appHcation based on shaping the particle structure (here fibers and ultrafine particles) in one of the gentle shaping processes characteristic to mnufacture of ^" DSP materials , using a Hquid vehicle to assist the shaping processes with subsequent exchange of the Hquid vehicle with a Hquid generating the matrix of the composite material.

^ JRE O PI

A typical process route is as foUows :

1. Shaping the fiber-particle structure assisted by a Hquid vehicle, e.g. water containing dispersing agent.

2. The shaping may consist of mixing fibers, ultrafine particles , and the Hquid vehicle, and casting the mass by a mechanical shear process such as rolling, pressing, or extrusion.

3. The shaping may consist of advanced fiber placement, typicaUy by filament winding of a single thread or net or web under simultaneous incorporation of vehicle-ultrafine particle- slurry, e . g. , by performing the winding submerged in the slurry. An example of a structure formed in this manner is shown in Fig. 5.

4. The shaping may be made by spray-up technique where fibers and slurry with ultrafine particles are placed simul¬ taneously .

5. Various types of additives may be used prior to or during the shaping process to protect the fibers and to ensure a good wetting and dispersion.

6. The vehicle Hquid is removed from the mass , typicaHy transported from the shaped hody in gaseous state achieved by lowering the relative vapour pressure of the Hquid vehicle in the surrounding environment by, e. g. heating, evacuation, or chemical or physical absorption of the vapour.

7. The vehicle Hquid may also be displaced by means of another Hquid, e.g. , by _, capHlary action, by dissolution, or -by pressure.

8. The volume between the particles occupied by the Hquid vehicle may be reduced by chemical reaction of the Hquid with the particles .

9. The voids between the particles are fHled with the matrix material on a Hquid form by infUtration (impregnation) , typicaUy as described in the present specification and in the specification of International Patent AppHcation No. PCT/ DK79/00047.

10. The Hquid is converted into sohd state by soHdification (typicaHy for metals and glass) or by polymerisation (typicaHy for polymer-forming monomers) controUed by thermal means , by chemical means , or by radioactive means .

This new type of high quaHty materials made possible by the present invention may, e . g. , be used as high performance rotor blades , and as parts of aeroplanes and space vehicles .

This aspect of the present invention may be defined as a shaped article comprising a matrix comprising fibers having a transverse dimention of less than 100 μm and bodies or particles of a size of from about 50 A to about 0.5 μm homogenously arranged and preferably substantiaHy densely packed in the voids between the. fibers, the fiber volume percentage of the matrix being at least 30%. In a preferred embodiment, the fiber volume percentage is at least 40%, preferably at least 50%, more preferably at least 50%, even more preferably at least 60%, and most preferably at least 70%.

According to a particular embodiment, the inter-particle substance (I) of such shaped articles is a metal or a plastics material.

Another- aspect of the present invention is a method for producing a shaped article, especiaHy a shaped article comprising a fiber- containing matrix showing any of the above characteristics , but also, quite generaHy, a shaped article comprising any of DSP matrix, said method comprising using a Hquid vehicle in the DSP shaping process and replacing the Hquid vehicle with another desired inter-particle substance in one or several stages .

FLY ASH

The preparation of particles A and B and their incorporation into the DSP material are aspects are of great practical significance for fly ash/cement-based DSP materials . The quaHty of DSP materials is strongly dependent on particle geometry and on the degree of the dispersion of the particles in the fresh materials .

Various methods of preparing the particles A, particles B and additional particles are avaUable, and various methods of preparing the fluid DSP materials are also avaUable. For DSP materials based on Portland cement or similar materials , the ultrafine particles A may typicaUy be produced by precipitation, condensation from a gas phase, or by particle comminution. One important source of ultrafine particles A and fine particles B is fly ash from power stations . The fly ash is developed as a dry powder, typicaUy coUected in filters . This material can be combined with the cement and any other constituent of the DSP material as a dry powder or as a mixture containing aU of or part of the DSP Hquid (typicaHy water plus dispersing agent) or mixed with possible additives and/or sand and/or stone and/or fibers (wet or dry) .

The fly ash may be improved for incorporation in DSP materials by adjusting the particle size and the particle size distribution of the fly ash by comminution and/or separation and/or removal of unde¬ sired chemical components .

The comminution may be performed by grinding.

Separation to obtain fly ash fractions useful for incorporation in

DSP materials may be performed by such methods as sieving, electrofHtering, flotation, techniques utilizing gravity and inertia in ^" Hquids (wet separation such as sedimentation or centrifugation) or air separation (such as by means of cyclones) . The methods mentioned may be combined in desired sequence .

When the fly ash is to be used in DSP materials, a typical fineness thereof corresponds to a specific surface area (Blaine) of at least

5000 cm 2 /g, in particular at least 7000 cm 2 /g and often at least

2

10000 cm /g. When a fly ash fraction of fine particle size has been obtained by a separation technique, the particles thereof are typicaUy substantiaHy spherical, and hence, one aspect of the invention comprises a fly ash fraction having a specific surface area as stated, the particles of the fly ash fraction being substan¬ tiaHy spherical.

A fly ash showing these characteristics is a very useful material for preparing DSP materials with cement or cement-like materials . Such fly ash may be shipped or transported by other suitable means , e.g. , transport in a pipeline, as a dry powder, as a Hquid slurry, in noduHzed form, as a press cake or in other forms known from powder technology.

As a general aspect of the present invention, the manufacturing and. preparation of ultrafine particles A and particles B for incor- poration into DSP materials may be performed by subdivision

(comminution) of larger particles (aggregates) or by growth of particles from gaseous or Hquid phase (or often as a combination by formation of the ultimate particles , e.g. , by precipitation foHowed by, e.g. , a milling process breaking down agglomerates of the ultimate particles formed) .

Particle subdivision may be obtained by mechanical means . One way is to prepare a dispersion in a Hquid medium involving one of or both of two general principles according to which a) the sohd particles in the Hquid medium are broken up (crushed, sheared, or attritioned) between two external surfaces or b) disruption occurs in the Hquid as the result of the mutual attrition between the particles themselves . In either case, the presence of a surface active agent may assist by reducing the breaking stress of the individual particles and/or by preventing re- aggregation .

Another way to achieve subdivision of particles is by simUar dry processes . Typical techniques are baH milling, coUoid milling,

OM

plastic milling (roHer miUs) , sand grinding, and high speed stone milling.

Quite generaHy, any method known from powder technology may be used for this purpose.

In case of subdivision and mechanical dispersion in a Hquid, it is desirable to use a highly viscous Hquid base to achieve a high shear stress at moderate rate of shear. Addition of a thickener may be very helpful.

Special types of particle comminution may be used to obtain extremely smaH particles. One method is particle comminution of the material to be used as source of particles, especiaHy as source of particles of the type A, together with other material which is not to be used as source for the particles A. This other aiding material serves to prevent reaggregation of the fine particles A during the subdivision and dispersing process . The aiding material should either be removed or used in other context in connection with the shaping of the desired bodies . For example, salt milling may be mentioned, where a large amount of salt is ground together with the material to form the particles A . The salt is then typicaUy removed by dissolution. Another new method is freeze grinding where a premix of the material to form the particles A (preferably pre-ground) and a grinding medium in Hquid state is frozen and then further ground as a sohd.

The particle comminution and dispersion may be achieved or contributed to during processes of mixing, transportation, and/or shaping.

Thus, the fine powder is typicaHy prepared (dispersed) in the hquid to be used in the later shaping process , and preferably also with the dispersing agents to be used in the later processes .

The particle dispersion may take place in connection with the mixing in any combination of the ingredients , e . g. ,

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1) ultrafine particles + Hquid

2) ultrafine particles + Hquid + dispersing agent

3) slurry as mentioned under 1) or 2) together with particles

C (typicaHy sand and stone)

4) ultrafine particles + any other sohd particles (B and/or C) with or without dispersing agent (the dispersing agent typicaHy being incorporated as a dry powder in this case) .

The dispersion may be achieved or contributed to in connection with the transportation, e.g. by high speed transportation of the fine powder combined with any of the other components in pipes, typicaUy driven by high pressure.

The dispersion may be achieved or contributed to during the shaping process, e.g. , extrusion, rolling, compression, vibrocomp action, ultrasonicaUy aided compaction, etc.

EspeciaHy, high shear processes such as extrusion and rolling are useful. But also the use of intensive vibration and ultrasonic treatment may assist the dispersion.

Other principles are to form particles by growth from gaseous or

Hquid state using any of the techniques described in the Hterature .

The production of ultrafine particles (particles A) may require several additional operations :

Particle separation may typicaUy be used to obtain the desired particle size and shape (and in case of the other particles also the desired type of particle (desired chemical, mineralogical, magnetic, structure, etc. )

Any of the usual techniques for particle separation may be used. In many processes where particles are formed by growth in a gas phase, e. g. , in the case of fly ash from a combustion process , it

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is desirable to perform the separation as closely connected to the formation process as possible (to avoid unnecessary agglomeration) .

Air separation technique using principles of electrical, thermal or convective forces may typicaUy be used. Thus, the coUection of fly ash from, e.g. , power plants by use of electrofUters or other filters seriaUy arranged permits the obtainment of fractionated fly ash.

Liquid separation may also be achieved, e.g, using sedimentation techniques, preferably aided by centrifugal techniques (typicaUy ultracentrifugation) .

AH separation processes may be strongly aided by the use of surface active agents preventing agglomeration and resulting in desired electrical surface charge.

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Example 1.

The materials used in this Example were as foHows :

White Portland cement: Specific surface (Blaine) 4380 cm /g

3 Density (expected) 3.15 g/cm .

SUica dust: Fine spherical SiO ₂ -rich dust. Specific surface (determined by BET technique)

2 about 250,000 cm /g, corresponding to an average particle diameter of 0.1 μ .

Density 2.22 g/cm ³ .

Bauxite: Refractory grade calcined bauxite, 85%

3 Al ₂ O ₃ , density 3.32 g/cm for sand

0 - 4 mm, 3.13 g/cm ³ for stone 4 - 10 mm.

Mighty: A so-caHed concrete superplasticizer, sodium salt of a highly condensed naphthalene sulphonic acid/formalde¬ hyde condensate, of which typicaHy more than 70% consist of molecules containing 7 or more naphthalene nuclei.

3 Density about 1.6 g/cm . AvaUable either as a sohd powder or as an aqueous solution (42% by weight of

Mighty, 58% by weight of water) ..

Water : Common tap water.

Preparation of cylindrical concrete specimens from wet concrete mixed with silica dust/cement binder and calcined bauxite sand and stone :

Concrete specimens were prepared from one 23 Hters batch of the foHowing composition :

SUica dust: 3200 g

White Portland cement: 16000 g

Bauxite 4 - 10 mm : 32750 g

Bauxite 0 - 4 mm: 10900 g

Mighty (powder) : 250 g

Water: 2980 g

Mixing

Coarse aggregate, cement and Mighty powder were dry -mixed in a 50 Hter paddle mixer for 5 minutes . Thereafter, the siHca dust was admixed, and mixing was continued for 10 minutes . The water was added, and the mixing was continued for approx. 10 minutes .

Fresh concrete

The concrete was soft and easHy workable.

Casting

6 concrete cylinders , diameter 10 cm, height 20 cm, and 2 slabs (40 x 30 x 5 cm) were cast at 20°C . The specimens were vibrated for 10 - 30 seconds on a standard vibrating table (50 Hz) .

Curing

Immediately subsequent to casting, the closed molds for the cylinders were submersed in water . t 60°C and cured for 5 days . The slabs were covered with plastic film and cured one day at

20°C in ah* after which they were submersed in water at 60°C and cured for 4 days . After curing, the specimens were demolded and stored in air at 20°C and approx. 70% relative humidity until testing (testing was performed within a period of 30 days subse- quent to the heat treatment) .

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Testing

Density, sound velocity, dynamic modulus of elasticity, compressive strength and stress/strain curve were determined for the 6 concrete cylinders (stress/strain curves were determined for two specimens only) .

In the table below, the test results are shown.

Table I

Properties of hardened concrete.

Density Sound velo¬ Dynamic mo¬ Compressive Static mo¬ city dulus of strength dulus of elasticity elasticity

2878 kg/m ³ 6150 m/sec. 109,000 MPa 217,5 MPa 78,000 MPa (standard deviation 6.2 MPa)

Stress/strain relationship for one of the cylinders is shown in Fig. 1, curve a. In the figure, for comparison, the stress/strain curve (curve c) for a corresponding specimen of normal quaHty concrete is shown (compressive strength 50.6 MPa) and for a specimen of high quaHty concrete in accordance with International

Patent AppHcation No . PCT/DK79/00047, prepared with the same type of high quaHty binder as used in the present example, but with-normal quartz sand and granite stone (curve b, compressive strength 130 MPa) .

OM

Example 2.

Experiments were made with various concrete superplasticizers in order to determine the water demand to obtain the fluid to plastic consistency of the mass to be cured.

The foUowing types of superplasticizers were used:

Mighty Vide Example 1.

Lomar-D A concrete superplasticizer of the same composition as Mighty, produced by Diamond Shamrock Chemical Company, N. Jersey, USA .

Mel ent An anionic melamine resin so¬ lution.

Betokem A sulphonic acid formaldehyde condensate based on naphthalene and Hgnosulphonate

Sikament A sulphonic acid formaldehyde condensate based on naphthalene

In aU the series, the foUowing common components were used (with reference to one batch) :

Quartz sand 1 - 4 mm 2763 g Quartz sand 0,25 - 1 mm 1380 g Quartz sand 0 - 25 mm 693 g Portland cement 2706 g SUica dust 645 g

The SPT-amounts were determined so that the content of dry matter was at least 82 g per mixture. A somewhat greater dosage was used with Betokem and Sikament. ^< glJRE

_ OMPI_ W .

The foUowing components were different:

Series 1 : Mighty solution (42%) 195 g

Additional water 437 g

Series 2: Lomar-D solution (37%) 221 g

Additional water 461 g

Series 3: Melment solution (20%) 410 g

Additional water 322 g

Series 4: Betokem solution (38%) 273 g

Additional water 431 g

Series 5 : Sikament solution (42%) 234 g

Additional water 464 g

Mixing.

The mixing was performed in a kneading machine with planetary movement, using a mixing blade. The foUowing procedure was foUowed:

1) Dry mixing of sand, cement + fiHer for 5 minutes

2) Addition of the major proportion of the water which does not form part of the concrete superplasticizer solution. About 50 ml of the water is kept for later use as rinsing water. Continued mixing for 5 minutes .

3) Addition of concrete superplasticizer solution with subsequent rinsing of the container with the above-mentioned 50 ml of water to secure that aH of the concrete superplasticizer is incorporated in the mixture. Mixing for about 10 minutes .

The water demands , that is, the amount of water used H the various mixes in order to obtain the specified consistency, were

-^U .

ascertained by trial mixing. The water demands appear from Table II below.

The consistency was evaluated by measuring the spreading of a cone of the material formed by pouring the material into a 5 cm high brass cone mould with bottom diameter 10 cm and upper diameter 7.1 cm on a flow table with brass surface for use in testing hydrauHc cement (ASTM C 230-368) and removing the mold. The diameter of the material was measured a) immediately sub¬ sequent to removal of the mold, b) after 10 strokes , and c) after 20 strokes .

The consistency was considered to be of the desired value for diameters of about 12 cm after 10 strokes and of 14 cm after 20 strokes .

Table II

Water demand (including water in the superplasticizer solution) expressed in grams of water per batch and in relation to the total amount of fine powder (cement + siHca dust) on a weight basis , the volume of fine powder being the same in aU of the mixes (1160 cm ³ ) .

Type of plasticizer Water demand

gram weight ratio water/cement + siHca dust

Mighty 550 - 0.16

Lomar-D 550 - 600 0.16 0.18

Melment 650 0.19

Betokem 550 - 600 0. 16 0.18

Sikament 550 - 600 0.16 0.18

Comments on the test results :

The experiments can be compared with the experiments in Example 7 in International Patent AppHcation No. PCT/DK79/00047, series 1, table V. Sand, cement, and siHca amounts are the same as in that example, the siHca dust and the cement, however, originating from later batches . Another difference is that in Example 7 of International Patent AppHcation No . PCT/D 79/00047, Mighty powder was used and was dissolved immediately prior to mixing, whereas in the present experiment a Mighty solution deHvered from the manufacturer was used. It wHl be noted that the water demand in aU cases with high dosage of superplasticizer was low, ranging from 500 g in Example 7 in International Patent AppHcation No . PCT/DK79/00047 to 600 - 650 g for Melment in the present experi- ment, corresponding to water/powder ratios of 0.15 - 0.19 by weight. This is to be compared with 1200 g of water and water/ powder ratios of 0.36 in mortar without superplasticizer. It wiH be noted that there are minor differences between the water demands of the various types of superplasticizer, Mighty being among the best. AH of the superplasticizers, however, appear to result in the extremely good flow properties of cement + siHca dust binder with very low water content, which are characteristic to the materials of the present invention and of International Patent AppH¬ cation No. PCT/DK79/00047.

Example 3.

Powder compaction of sand and stone.

The purpose is to evaluate the resistance of various sand and stone materials to deformation on powder compaction , and in particular, to compare natural concrete aggregates with particu¬ larly strong and hard materials .

__O PΓ ^" wϊ ^p

Materials .

Quartz sand 0.25 - 1 mm, quartz sand 1 - 4 mm, crushed granite 4 - 8 mm, refractory grade bauxite 0 - 4 mm, refractory grade bauxite 4 - 10 mm, sHicon carbide 0.5 - 2 mm (Qual. 10/F PS - K

Arendal Smeltevaerk A/S , Ejdenhavn, Norway) .

Comments .

The individual fractions of particles are relatively uniformly grad¬ uated, corresponding to the ratio between the largest and the smaHest grain size (particle size) substantiaHy not exceeding 4.

Powder Compaction.

Samples of the individual sand and stone fractions were compressed by uniaxial die pressing. The compaction equipment consists of a cylindrical die cylinder open in both ends , and two cylindrical pistons (diameter of the die cylinder 30 mm, powder height on filling about 32 mm and after finished compression 16 - 23 mm depending upon the type of powder) .

Dry materials were poured loosely in the die cylinder. The compac¬ tion was performed in an Instron testing machine having constant compaction rate (5 m /min . ) up to a compaction pressure of 350

MPa, whereafter the pressure was released by moving the piston in opposite direction. During the compaction and release, force/ - displace ent curves were plotted.

Results .

From the curves of force/displacement, comparisons of compaction pressure to obtain identical "density" was performed for the indi¬ vidual materials . The results appear from Table III below.

-^TJREXg-

Table III

Compaction pressure, MPa, as a function of the degree of com¬ paction. The degree of compaction is the ratio between the volume of the particles and the volume of the total powder mass (expressed in another way: 1 - porosity) .

Degree of Granite Quartz Quartz Bauxite Bauxite SHicon

Carbide compaction 4-8mm l-4mm 0 .25-lmm 4- 10mm 0-2mm 0.5- 2mm

0.70 16 10 24 36 61 48

0.75 29 23 42 61 110 82

0.80 59 43 76 95 194 ^• 145

It wiH be noted that the compaction pressure to obtain same degree of compaction is considerably higher for the hard materials (bauxite and silicon carbide) than for materials usuaUy used as additives in concrete (granite and quartz) .

Comment:

The powder compaction technique is suitable for comparing the strength of particles, provided the various particle materials or particle compositions have about the same particle geometry and provided that the particle size is relatively large in comparison with the dimensions of the die cylinder. These conditions have been reasonably fuHHled in the experiments with quartz sand and fine -bauxite (in these cases , the particles are compact, rounded and smaH) . In the experiments with granite stone and coarse baux- ite, the particle/die ratio was somewhat too large (about 0.2 - 0.3) for permitting a direct comparison between the results of the test with quartz sand and with fine bauxite. On the other hand, mutual comparison of the two is reasonable. It is difficult to compare the

- jR

OMPI

results of the experiments with siHcon carbide with the remaining results, considering that this powder material, in contrast to aU the other materials, had very sharp edges .

Example 4.

High QuaHty Mortar.

Two different types of mortar mixes were prepared, both on the basis of low alkaH sulphate resistant Portland cement, sUica dust, and Mighty, but with different types of sands, namely refractory bauxite and siHcon carbide (Qual. 10/F PS - K, Arendal S elte- vasrk A/S, Ejdenhavn, Norway) . The purpose was to investigate mechanical properties of mortar made with very strong sand, com¬ pare Example 3, and with the very strong sUica/cement binder described in International Patent AppHcation No . PCT/DK79/00047. In aU the mixes , the foUowing common components were used (with reference to one batch) :

SUica dust 645 g Low alkaH sulphate resistent Portland cement 2706 g

42% Mighty solution 195 g

For the bauxite mortar, the foHowing components are used:

Bauxite 0 - 4 mm 6104 g Water (excluding water in the Mighty solution) . 387 g

For mortar with siHcon carbide the foUowing components were used:

SHicon carbide 5755 g Water (excluding water in the

Mighty solution) 487 g

The amounts of sand, cement and Mighty used (after volume) are the same as the amounts used in Example 9 in International Patent AppHcation No. PCT/DK79/00047. In the mortar with bauxite, the water amount was also the same as in Example 9 in International Patent AppHcation No . PCT/DK79/ 00047, whereas the water amount in the mortar with siHcon carbide was considerably higher. This was due to the fact that the silicon carbide sand had very sharp edges and therefore required a more easHy flowable sUica/cement paste and/or a larger amount (by volume) of paste.

For each of the two types of mortar, two batches were prepared, one having the composition as stated above, the other one of double size.

Mixing and Casting.

The mixing was performed in a kneading machine with planetary movement, using a mixing blade. The foHowing procedure was f oUowed :

1) Dry mixing of sand, cement + fiHer for 5 minutes .

2) Addition of the major proportion of the water which does not form part of the concrete superplasticizer solution . About 50 ml of the water is kept for later use as rinsing water. Con¬ tinued mixing for 5 minutes .

3) Addition of concrete superplasticizer solution with subsequent rinsing of the container with the above-mentioned 50 ml of water to secure that aU of the concrete superplasticizer is incorporated in mixture. Mixing for about 10 minutes .

The mortar mixtures behaved like highly viscous fluids and were cast in cylindrical molds (height 20 cm, diameter 10 cm) on a stan- dard vibrating table (50 Hz) . The casting time was about 1 minute.

The specimens (in closed molds) were cured in water at 80° C for 4 days .

Testing.

Density, sound velocity, dynamic modulus of elasticity, compres¬ sive strength and stress/strain curve were determined. The com¬ pressive strength and the stress/strain curves were determined on a 500 tons hydrauHc press using a rate of stress change of 0.5 MPa per second. The results obtained appear from Table IV :

Table IV

Properties of cured mortar evaluated by measurement on cylindric specimens (height 20 cm, diameter 10 cm) .

Bauxite Mortar SHicon Carbide Mortar

Density (kg/m ) 2640 (6)*)

2853 (6)*- Sound velocity m/sec. 6449 (6) *) 6443 (6)*) Dynamic modulus of elasticity MPa 118600 (6) ) 109600 (6)*- Compressive strength and its standard deviation (MPa) 248.0 SD 7.7 184.3 SD 5.9 (6)* (4)*

*) = number of tests .

Stress/strain measurements were performed on two specimens from each series . The samples were loaded to about 60% of then ^* rupture of load and were thereafter released, whereafter they were again loaded up to rupture without recording of stress/strain . A few of the samples were loaded and released several times .

The stress/strain curve for the bauxite mortar was practicaHy a straight line throughout the complete measuring range (0 - 150 or 160 MPa) with a slope (secant) corresponding to a modulus of elasticity of 84300 MPa. On repeated loading and unloading, only insignificant hysteresis was noted.

The stress/strain curves for the mortar with siHcon carbide (measuring range 0 - 100 MPa) bent somewhat with initial slope corresponding to a modulus of elasticity of 86000 MPa and modulus of elasticity at the pressure of 100 MPa of 72000 MPa. On repeated loading of 100/120/140/160 MPa, a specimen of the siHcon carbide mortar showed marked hysteresis indicating internal structure deterioration .

The compressive strength for mortars with bauxite did not seem to be significantly influenced by pre-loading up to 150 - 160 MPa, whereas the strength of the mortar with sHicon carbide was consi¬ derably lower for the samples which have been previously loaded.

The values of the compressive strength for the pre-loaded speci- mens of the sHicon carbide mortar were, therefore, not included in the results in Table IV.

Comments on the results .

It wiH be noted that the mortar with bauxite sand is extremely strong and rigid, having compressive strengths of 248 MPa (maxi¬ mum value for two of the specimens were 254.2 MPa corresponding to a load of more than 200 tons) . The rupture proceeded to a- large extend through the bauxite sand, indicating the possibHity of producing even stronger mortar by utilization of even stronger sand materials .

The compressive strength of the mortar with sHicon carbide was considerably lower (184.3 MPa) and is not much higher than for ^' the .corresponding mortar containing quartz sand (160 - 179 MPa, cf . International Patent AppHcation No. PCT/DK79/00047 , Example 9) which might seem strange in view of the great hardness and strength of sHicon carbide per se. The reason is undoubtedly that the mortar with siHcon carbide used considerably more water than the mortar with bauxite and the mortar with quartz sand referred to in International Patent AppHcation No. PCT/DK79/00047. This results in a considerably weaker binder. The water/powder ratio

(total water in relation to cement + silica by weight) was 0.149 for

- EXC

the bauxite or quartz mortars and 0. 179 for the siHcon carbide mortar. The rupture proceeded to a large extend outside the sHicon carbide particles . This, compared with the bended stress/ strain curve and the large hysteresis (which is characteristic to brittle materials where the particles are considerably stronger than the matrix) indicate the possibility of obtaining considerably higher strength by improving the matrix. This can be achieved by reduc¬ ing the water /powder ratio to, e.g. , 0.13 - 0.15, which is possible by using a somewhat coarser siHcon carbide sand and/or larger amount of cement and sUica.

Additional 16 cylinders of the bauxite mortar have been prepared with the same composition and using the same technique as above with the exception that the bauxite was from a later batch.

The purpose was to examine various mechanical properties . At first, density, sound velocity and dynamic modulus of elasticity were determined on aH 16 specimens . As a guidance, the tensHe strength was determined on two of the specimens .

The results are shown below.

Density 2857 kg/m ³

Sound velocity 6153 m/second Dynamic modulus of elasticity 108, 200 MPa

Compressive strength 261.1 MPa

268.1 MPa

Comments on the test results .

The same density as above was found, whHe sound velocity and dynamic modulus of elasticity were somewhat lower. The reason for this is unknown, but is beHeved to be due to an error in the determination of the time for travelling of sound impulse (either in the test on page 65 or the test above),.

- J EAlT

The strengths were sHghtly higher than above. The highest value of 268.1 MPa corresponds to a load of 214.6 tons and a pressure of 2732 kg/cm ² .

Example 5.

High quaHty bauxite mortar.

A bauxite mortar was prepared having the same composition and using the same technique as mentioned in Example 4 with- the exceptions

1) that the bauxite was from a larger supply, 2) that the size of each batch was twice that appHed according to

Example 4, and

3) the specimens were aUowed to stand from a few days up to H year after heat-curing (four days at 80°C) in 20°C at 70°C relative humidity.

From each of the four batches 4 cylinders (height 20 cm, ^" diameter 10 cm) were cast.

Testing.

Density, sound velocity, dynamic modulus of elasticity and stress/- strain curve were determined using the technique described in Example 4.

The results appear from below Table V.

Table V.

Properties of cured bauxite mortar by measurement on cylindrical specimens (height 20 cm, diameter 10 cm) .

3 Density kg/m 2857 SD 8 (lδ)

Sound velocity m/sec. 6153 SD 36 (16)

Dynamic modulus of elasticity Mpa 108156 SD 1426 (16)

Compressive strength MPa 268.3 SD 7.5 (14)

The stress/strain curve is shown in Fig. 14 together with a similar curve for ordinary concrete normaUy considered to be of very high quaHty (compressive strength 72 MPa) .

It is seen that the bauxite-cement-sHica mortar has a compressive strength (270 MPa) approximately four times higher than that of traditional high quaHty concrete and a modulus of elasticity (slope of the curve) approx. twice as high.

One of the specimens had a compressive strength of 282.7 MPa and

3 a density of 2861 kg/m which corresponds to a stress/density-ratio

2 of 98812 (m/s) . The load of the cylinder corresponds to the base load of a 10076 meter high prism prepared from the material.

(By way of comparison it may be mentioned that the yield load of high quaHty structural steel (400 MPa) corresponds to the base- load of a 5200 meter high steel prism. )

Example 6.

DurabHity of edge beams .

In tests of the durabHity of edge beams made for the Danish

Highway Department (Vejdirektoratet) it was found that edge beams of DSP materials completely survived a severe frost-thaw test which

destroys traditional high quaHty concrete. As described in "Forsøg med Kantelementer af fiber- og siHcabeton, Rapport over forunder- søgelser og udførelse" , December 1980, Cowiconsult, Denmark, the foUowing test was made: .

5 types of concrete were tested of which 3 were DSP concrete

TM (DENSIT from Aktieselskabet Aalborg Portland- Cement-Fabrik) and 2 were traditional high quaHty concrete. 15 edge beams were prepared having dimensions about 1 x 1 x 4.5 meters) .

Concrete type 1 was a traditional concrete which is today con¬ sidered appHcable for bridge edge beams. The composition of the concrete type 1 was as foHows :

Cement 330 kg/m ^'

Water 125 It

Sand 760 I!

Stone 4/8 mm 190 II

Stone 8/16 mm 950 II

Addition of air (Sika-Aer) 0.4 11

Plasticizer (Sikament) 3.3 It w/c (water/cement) 0.38 II

Concrete type 2 was a fiber concrete with a fiber content of 1.75 per cent/volume. The composition of the concrete type 2 was as f oHows :

Cement 450 1 cg/m ^'

Fly ash 180 II Water 260 It

Sand 745 II

Stone 4/8 mm 320 II

Concrete adhesive, (Betof lex- super) 27 " ( (approx . 50%

Fibers 16 II dry matter) w/c (water/cement) approx. 0.60 It w/p (water /powder) • approx. 0.45 It

Concrete type 3 (1.25% fiber concrete) was a fiber-DSP-concrete with a fiber content of 1.25 per cent/volume. The composition of the concrete type 3 was as foHows :

Cement 500 kg/m°

Fly ash 225 "

SHica 75 "

Water 180 "

Sand 750 "

Stone 4/8 mm 500 "

Superplasticizer (Mighty) 28 " (approx. 42% dry matter)

Fibers 11 " w/c (water/cement) 0.40 " w/p (water/powder) 0.25 " .

(Powder: cement + fly ash + siHca)

Concrete type 4 (20% siHca concrete) was a DSP concrete with a siHca content of 20% of the weight of the cement. The composition of the concrete type 4 was as foHows :

Cement 500 kg/in

Silica 100 tl

Water 95 II

Sand 670 It

Stone 4/8 mm 370 II

Stone 8/18 mm 730 II

Superplasticizer (Mighty) 32 " (approx. 42% dry matter) w/c (water/cement) approx. 0.23 II w/p (water/powder) appro . 0.19 It

Concrete type 5 was a DSP concrete with a siHca content of 50% of the weight of the cement. This amount of siHca in relation to the weight of the cement is extreme, and the purpose of testing this concrete type has primarily been to find possible negative effects of such a high addition of silica. The composition of the concrete type 5 was as foHows :

-^ REA^

Cement 220 : kg/m°

SHica 110 It

Water 80 tt

Sand 750 It

Stone 4/8 mm 450 II

Stone 8/18 890 II

Addition of air (Sika-Aer) 0.4 II

Superplasticizer (Cem-mix) 33 " (approx. 42% dry matter) w/c (water/cement) approx. 0.45 It w/p (water/powder) approx . 0.30 It

Cement

Ordinary low alkaH sulphate resistant Portland cement PC(A/L/S) .

Fly ash.

The fly ash was from the "Fynsvaerket" power plant.

SUica.

The sHica was from Elkem Spigerverket in Norway (the silica was of the same type as used in the previous example, i. e. with a

2 specific surface of about 250,000 cm /g and a density of about

2200 kg/m ³ ) .

Sand.

Holbaek sea gravel. The sand was examined at the State Testing Laboratory and the Danish Technological Institute.

Stone .

Dalby granite in the fractions 4/8 mm and 8/18 mm. The stones were examined at the State Testing Laboratory.

" E O PI

Fibers .

® Krenit -fibers (polypropylene fibers) , length 12 mm, from Jacob

Holm Varde A/S , Denmark.

The fibers were made from polypropylene film stretched in a ratio of about 1:17 and fibriUated on a needle roUer in analogy with Example 4 in International Patent AppHcation No . PCT/DK79/00047.

Castings of beams .

AH the concrete for the beam castings was mixed in a 1200 Hters paddle mixer. The dosage of aggregate and cement was performed "manuaUy". The concrete was transported in a concrete bucket from the mixer to the beam mold.

The beams were cast upside down and were thus cast against a mold on aU future up-turned and vertical sides . The mold was made of steel. Vibration was estabHshed partly by means of a vibration table, on which the molds were placed, and partly by means of a poker vibrator.

During the casting and the whole curing period the beams were wrapped in strong plastic foH to protect them against drying out. They were stored firstly in a casting haU and secondly outdoors during the last part of the casting period.

Concrete data.

Concrete type 1 , ordinary concrete: Cylinder compressive strength about

2 65 MN/m (28 days water storage) .

Concrete type 2, 2.0% fiber concrete: Cylinder compressive strength about

2 25 MN/m (28 days water storage)

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Concrete type 3, 1.25% fiber concrete: Cylinder compressive strength about 80 MN/m (28 days water storage)

Concrete type 4, high strength siHca: Cylinder compressive strength about

2 130 MN/m (28 days water storage)

Concrete type 5, normal strength siHca: Cylinder compressive strength about

2 100 MN/m (28 days water storage)

Besides, three sawed out prisms having the dimensions 30 x 30 x 70 mm were prepared from each concrete type.

Frost- thaw- thawsalt test.

Frost testing and thawsalt strain test were made on three sawed out prisms of 30 x 30 x 70 mm according to the foHowing method:

On each of the four long sides of the prisms two 50 mm spaced measuring taps were glued. After water storage for one week the prisms were exposed to the foHowing tests :

1) 10 minutes Hi water at 18 - 20°C,

2) 20 minutes in a saturated solution of NaCl at -15°C, and

3) items 1) and 2) were repeated.

The lengths of the prisms (the distance between the measuring points) were measured about every 50 cycles .

The total length changes , millimeter per meter (mm/m) , of the five concrete types appear from the below table :

Table

Number of cycles

Concrete 96 241 337

Total length changes mm/m mm/m mm/m 1 Cracked after 44 cycles 2 3.3 5.8 6.5 3 0.1

4 . 0.2 5 0.2

As appears from the table concrete type 1 (ordinary concrete) was not resistant to the testing and neither was concrete type 2 which, due to the fibers , was stHl coherent and practicaUy without visible craks . However, some crumbling can be observed in the surface.

Concrete types 3, 4 and 5 were practicaUy unaffected by the tests .

Test results .

Concrete type 1, ordinary concrete:

The concrete showed a very poor resistance to the frost- thaw- thawsalt test as it cracked shortly after.

Concrete type 2, fiber concrete:

The resistance of the concrete to the frost-thaw-thawsalt test was insufficient but due to the fiber reinforcement the - -concrete showed a good coherence.

Concrete type 3, fiber-DSP-concrete with siHca, concrete type 4, fiber-DSP-concrete with high strength siHca and concrete type 5 , fiber-DSP-concrete with normal strength siHca were not influenced by the frost-thaw-thawsalt test.

-ftO EATT

Comments on the results:

The experiments show that the DSP materials (DENSIT TM -concrete

Nos. 3, 4 and 5) have a high frost resistance (no deformation at aU) in a severe frost/thaw test which destroys ordinary high quaHty concrete.

In the drawing,

Figs . 1, 2, 3, 4 and 5 are enlarged sectional views Illustrating various DSP systems comprising densely packed bodies Fig. 3 is an enlarged partiaHy sectional view Illustrating a DSP system comprising densely packed compressible bodies,

Figs . 6 and 7 are enlarged sectional views Illustrating the behaviour of cement particles in normal concrete,

Fig. 8 is a further enlarged sectional view iUustrating cement particles in DSP,

Fig. 9 is an enlarged sectional view iUustrating anchoring of a reinforcing fiber in a DSP matrix,

Fig. 10 is a sectional view iUustrating the internal coherence of a

DSP paste and its resistance to being entrained with flowing water, Fig. 11 is a sectional view illustrating the use of DSP in practice for an otherwise difficult repair of a concrete structure under streaming water,

Fig. 12 is a sectional view Illustrating the utHization of DSP in practice for repair of a concrete waH where there was only unilateral admission for introduction of the repair material,

Fig. 13 is a sectional view Illustrating the utHization of the easy flowing properties of DSP for estabhshing an internal DSP coating in a curved tube,

Fig. 14 is a stress-strain diagram for ordinary high strength concrete and DSP containing refractory grade bauxite, respectively,

Figs . 15 through 17 are sectional views Illustrating drained compression,

Fig. 18 is a perspective view Illustrating the production of a panel-shaped body which may optionaHy be subjected to further shaping,

Figs . 19 and 20 are perspective views iUustrating the shaping of a tube section from a panel-shaped body,

Fig. 21 is a perspective view iUustrating the utHization of extrusion in the production of DSP-encapsulated electrical components,

Figs . 22 and 23 are sectional views illustrating the use of DSP for compression moulding like a plastics material,

_/ ^ ZE

Fig. 24 is a perspective view iUustrating the production of panel- shaped reinforced articles, e.g. , waU or roof elements, by superimposing roUed panels of DSP,

Fig. 25 is a perspective view Illustrating the production of a sandwich element from two sheets roHed fiber reinforced material where the fiber orientation of one layer in the sandwich is perpendicular to the fiber orientation in the other layer, Fig. 26 is a perspective view iUustrating the principle of estabhshing a panel-shaped element from two panels between which sanitary instaHations or the like are embedded,

Fig. 27 is a perspective view iUustrating the lower element of a simUar element as in Fig. 26, but with incorporated tubing for floor heating or electrical instaUation, Fig. 28 is a perspective view iUustrating the mass production of tiles or bricks or the like from a sheet of DSP,

Fig. 29 is a perspective view iUustrating a roUer for rolling DSP Fig. 30 is a perspective view iUustrating the production of corrugated roof panels from DSP using a speciaUy shaped roHer Fig. 31 is a perspective view iUustrating the production of a waH or roof panel from a DSP material, also using a speciaUy shaped roUer

Fig. 32 is a sectional view iUustrating underwater reproduction casting of DSP under streaming water, Fig. 33 is a perspective view iUustrating reproduction casting of, e.g. , a complete area comprsing archeological objects,

Fig. 34 is a perspective view iUustrating the molding of an extruder die,

Figs. 35 and 36 are sectional views iUustrating a molding system for preparing bodies of fluid DSP, Fig. 37 is a sectional view IUustrating a material comprising smaU particles packed against larger bodies,

Figs . 38 - 40 are sectional views IUustrating a tool for shaping of steel' panels, e. g. for automobUe body parts , both the matrix part and the patrix part of the tool being made from high compressive strength DSP material,

Fig. 41 is a sectional view Illustrating the injection of a DSP paste containing fibers orientated substantiaHy in the direction of movement, _/ ^ JREA

[ OMPI

Fig. 42 is a cross-sectional view of a channel with connected fis¬ sures and cavities into which a fine DSP material has been pre-injected and has penetrated into and fHled the fissures and cavities , whereafter the fine DSP grout has been replaced with coarse DSP which has replaced the fine DSP and now fUls the bulk of the cavity,

Fig. 43 is a sectional view Ulustrating the waH effect, the packing density of the particles in the narrow zone near the waH being smaHer than in the bulk, in the interface between a waU and normal concrete,

Fig. 44 is a sectional view Ulustrating an injection into a channel of first fine DSP grout, and thereafter a coarse DSP grout, Fig. 45 is a sectional view Ulustrating the same injection as in Fig. 44, and showing how air in fissures and cavities associated with the channel is entrained with and replaced by the injected fine

DSP,

Fig. 46 is a sectional view iUustrating injection of a ternary com¬ bination comprising first a Hquid, then fine DSP, and then a coarse DSP grout, Fig. 47 is a sectional view Ulustrating how a wetted surface aUows a closer packing of DSP in interstices,

Fig. 48 is a sectional view Illustrating the arrangement of particles in a cavity by sedimentation, Fig. 49 is a perspective view Ulustrating the grouting of a duct with a cable used for post-tensioned concrete members .

Fig. 50 is a cross-sectional view of the duct shown in Fig. 49 where fine DSP secures a complete filling of the interstices around the cable, Figs . 51 and 52 are cross-sections of suitable cable and duct con- structions where infUtration is facilitated by means of fins or spacers ,

Figs . 53 and 54 are sectional views Ulustrating problems associated with ^' peeling of wet DSP paste used as a surface coating material, Figs . 55 is a perspective view Ulustrating surface cotaing of an article by applying a layer of fiber- supported extruded DSP on the article ,

Fig. 56 is a sectional view Illustrating the appHcation of a DSP coating on the interior surface of a tube,

^« REA tT

Figs . 57 through 61 are sectional views Ulustrating the principle of preparing high quaHty foam,

Fig. 62 is an enlarged section Ulustrating the principle of the high quaHty foam preparation shown in Figs. 57 through 61, Figs . 63 and 64 are sectional views iUustrating the preparation of a high quaHty foam material,

Figs . 65 and 66 are sectional views iUustrating the preparation of a material having longitudinal cavities by casting in a cavity wherein elastic bands are suspended at high tension and are thereafter released to estabhsh densely packed paraUel pores ,

Fig. 67 is a sectional view Ulustrating the winding of an elastic material under tension and submerged in a slurry of ultrafine par¬ ticles to estabhsh a structure which may be additionaHy densified by releasing the tension, the structure estabhshing densely packed paraUel pores when the elastic material is removed after setting of the slurry,

Fig. 68 is a sectional view Illustrating the utHization of special ultrafine particles to increase the quaHty of the system constituted by the bodies A, Fig. 69 is a diagram which illustrates the- possible maximum size of ideaUy shaped taU buHdings made from high quaHty concrete, structural steel, normal DSP, and high quaHty DSP, respectively, Fig. 70 Hlustrates the span of an arc-curved bending member possible with high quaHty concrete and with normal DSP, respectively,

Fig. 71 Hlustrates the relation between the necessary thicknesses of a bending member of high quaHty concrete and a bending mem¬ ber of the same length made in high quaHty DSP, respectively, the bending members being loaded with their own weight, Fig. 72 is a sectional view Ulustrating a bridge construction with dimensions made possible by the use of high quaHty DSP, com¬ pared to the dimensions possible with ordinary high quaHty con¬ crete, Fig. 73 is a diagram Ulustrating strength/density ratio of various materials ,

Fig. 74 is a diagram Illustrating maximum span related to minimum thickness for various materials,

Fig. 75 Hlustrates prismatic bending members , and Fig. 76 Hlustrates part of a bridge span.

Reference is made to the drawing, where like numerals generaHy designate like parts .

In Fig. 1, which Illustrates a typical DSP matrix structure 10, 12 designates substantiaHy densely packed particles B , e . g. , Portland cement particles , and 14 designates homogeneously arranged and optionaHy densely packed particles A, e . g. , particles of sHica dust homogeneously dispersed in water by means of a concrete super¬ plasticizer, or a coherent unitary structure formed from such par¬ ticles and from sohd inter-particle substance formed by chemical reaction between solutes generating from the cement particles . The system shown in Fig. 1 has typicaUy been estabhshed by gentle mechanical means, e.g. by shear or vibration, or simpty under the influence of gravity.

In Fig. 2, the particles B (12) comprise larger particles and smaHer particles, with gap grading between the particles B . The system of Fig. 2 has typicaHy been estabhshed using the same means as described in connection with Fig. 1.

However, in Figs . 1 and 2, 14 may also designate ultra fine par- tides which have been homogeneously arranged by means of a surface active agent in accordance with the fluid DSP system estabhshment processes of the invention, but which are now surrounded by an inter-particle substance which is different from the fluid by means of which the particles were arranged and which has been introduced by exchange of the original fluid by infU¬ tration .

In ^" Fig. 3, compressible bodies 12, e. g. polystyrene spheres con¬ stitute the densely packed particles B , and homogeneously arranged or densely packed particles A, typicaHy rigid smaH particles surrounded by inter-particle substance, fiH the voids between the adjacent densely packed gas bodies B . However, Fig. 3 also Hlustrates the case where the bodies 12 are compressible

bodies of a larger size than the particle B size, and 14 is a soH¬ dified DSP paste which, in itself, comprises substantiaHy densely packed particles B with homogenously arranged and optionaHy densely packed particles A and inter-particle substance in the voids between the particles B , the DSP paste, hence, having a structure as Hlustrated in Fig. 1 or Fig. 2.

In Fig. 4, fibers or elongated particles 12 constitute the densely packed bodies B , and homogeneously arranged and optionaHy densely packed particles A in inter-particle substance fiH the voids between the densely packed bodies B . In this case, the dense packing of the bodies B refers to dense packing as obtained by simple mixing and casting with the maximum fiber load Hmited by the mixing and shaping process only. Also in this case, the inter-particle substance may be a substance which is different from the fluid by means of which the particles were arranged, the inter-particle substance now present being a substance introduced by exchange of the original fluid by infUtration .

In Fig. 5, the densely packed fibers or elongated bodies 12 show a dense packing of bodies B referring to a most efficient manner of estabHshing dense packing of non-compressible fibers : paraUel placing of the elongated bodies or fibers with homogeneously arranged and optionaHy densely packed particles A in the interspace between the densely packed bodies B . This structure has been established, e.g. , by filament winding of the fibers 12 immersed in a slurry of homogenously dispersed and optionaHy densely packed particles A. The structure shown in Fig. 5 is typical of the structure desired in ultra high quaHty, highly fiber-loaded stress and abrasion resistant materials where the inter-particle fluid between particles A which are , e . g. , densely packed microfine metal particles , has been replaced, by infUtration, with a strong inter-particle substance, e . g. , a metal or a polymer.

In Fig. 6, Portland cement particles 16 form an open flocculant structure in an aqueous phase in the absence of surface active agents .

"^Hi X

Fig. 7 Hlustrates how such a system wiH normaUy show a tendency to sedimentation of the cement particles when the flocculating ten¬ dency is eliminated by means of a superplasticizer.

Fig. 8 Hlustrates, in further enlarged scale, a DSP paste system, e.g. a cement/ultrafine siHca system with superplasticizer where the voids between the cement particles 12 are fiHed with a suspen¬ sion of ultraltrafine siHca particles 18 which are substantiaHy densely packed in the suspension . 20 designates the inter-particle substance, in this case, e. g. , superplasticizer solution. In such a system, the tendency to sedimentation of the particles is minimized due to the extremely slow water flow around the ultrafine particles in accordance with classical hydrodynamics .

Fig. 9 Hlustrates a fine reinforcing fiber 22 embedded in a DSP matrix 10, e.g. , a cement-based DSP matrix. By using such a cement-based DSP matrix instead of ordinary cement paste, the mechanical fixation of the reinforcement is increased even more than the strength, this increase being one or several orders of magnitude. This is because the dimensions of the "roughness" or

"wave configuration" of the fiber which are necessary to obtain "mechanical locking" of the fiber H the matrix are reduced one to two orders of magnitude, which also means that in the DSP matrix, it becomes possible to obtain mechanical locking of fibers which are one to two orders of magnitude smaHer than the smaHest fibers which can be mechanicaUy locked in ordinary cement paste .

Fig. 10 demonstrates the surprising internal coherence of the fresh fluid to plastic cement-based DSP mortar 24 placed on a supporting glass plate 26 under vibration (50 Hz - 10 s) and then kept under flowing tap water (rate of outflow about 4 Hters per minute) . In this demonstration, the mortar is typicaHy kept under the flowing wa ^' ter for periods of 2 - 30 minutes without any visible washing out of the components thereof . The mortar was prepared as described in Example 9 of International Patent AppHcation No.

PCT/DK79/00047.

Fig. 11 Hlustrates the repair of a bridge construction 28 in flowing water 30 a river by underwater injection . Between a base struc¬ ture 34 of ordinary concrete 36 and a foundation 38, erosion ca¬ vities 40 had exposed wood pHes 32, incurring danger of severe damage of the pHes . EasHy flowing cement-based DSP paste 24 was pumped through one of drilled holes 42 into the cavity 40. Due to its higher density, the DSP paste displaced water from the cavity 40 and rose into the remaining holes 42, completely filling the cavity and the holes and forming a new cover, also on top of the foundation. AH casting was performed under water, and the river flow over the freshly case DSP concrete, which, however, had such a high degree of internal coherence that substantiaHy no washing out occurred.

Fig. 12 Hlustrates the repair of a waH element 44 of a sub water tunnel under a bay. An easHy flowable DSP material 24 was fiHed into the cavity to be repaired. The cavity had a compHcated shape and was heavHy reinforced with steel reinforcement 46. The DSP material was introduced from one side through a hose 50 and rose at the other side of and existing concrete waH 36 and fiHed the cavity between the concrete waH and formwork 48.

Fig. 13 Hlustrates casting of a Hning of high abrasion resistance inside a steel pipe 52 used for transportation of powder (coal) . A plastic tube 54 fiUed with sand 56 was placed in the interior of the pipe and was kept in position by means of bracings 58. A steel fiber-reinforced DSP material 24 based on Portland cement and refractory grade bauxite was poured into the pipe 52 under shght external vibration and completely fiHed the space between the steel pipe 52 and the inserted plastic tube 54. After curing of the DSP material, the sand was removed, and the plastic tube was puHed out.

Fig. 14 is a stress- strain diagram recorded during compression testing of 10 cm diameter, 20 cm high cylinders of ordinary high quaHty concrete and DSP mortar with sand consisting of up to 4 mm refractory grade bauxite, respectively . The DSP material was

TM DE SIT-S from Aaϊborg Portland, Aalborg, Denmark. _____

The compression strengths measured were 72 and 270 MPa, re¬ spectively .

Figs . 15, 16, and 17 Hlustrate compaction of DSP concrete or mortar in a vessel 62 where a surplus of fluid DSP paste 68 is squeezed out of the mass and flows past aggregates 64 and the passage between a piston 66 and the waH of the vessel 62 as the piston is moved down . Hereby (Fig. 16) , the aggregate skeleton is compressed. After compression, the surplus of paste is removed (stiH with load on the piston) . Hereafter, the piston is removed, and the aggregate skeleton expands sHghtly (elastic spring back) , pulling the paste 68 sHghtly into the voids (a suction) whereby inwardly curved paste/gas interfaces are formed, which, due to surface forces , stabilize the compacted drained material.

Fig. 18 Hlustrates rolling of a plastic DSP material 68 by means of a pair of roHers 70 of an elastic material with a spacer member 72 inserted between the roHers to form a semi-manufactured plate or sheet of DSP material which may be further shaped.

Figs . 19 and 20 Hlustrate the shaping of such a semi-manufacture plate or sheet 74 between halves 76 of a compression mold (which may in themselves be made from a DSP material) to form a tube section 80.

Fig. 21 Hlustrates the extrusion of a DSP material. From an ex¬ truder die 82, an extruded string 84 of DSP material passes a support 86 where electrical components 88, e. g. resistance com¬ ponents , are inserted into the V-shaped extruded string. The string is cut by means of a cutter 90, and the resultingsections 92 are thereafter compressed in a compression mold 76 to form DSP-encapsulated components 94.

Fig. 22 Hlustrates compression shaping of DSP material 68 between a lower and an upper mold part 96 and 98, respectively, and Fig.

23 Hlustrates the compression shaping of a large kitchen table/wash basin element from DSP material 68 in a large mold 100, 102.

Fig. 24 Hlustrates the preparation of a reinforced DSP panel member by compaction of fresh roHed plates 110 and 112 of cement-based DSP on each side of a steel reinforcing grid 108 in a press 104, 106.

Fig. 25 Hlustrates the preparation of a sandwich element of fiber-reinforced DSP material where the fiber orientation in the ^" upper component 110 is perpendicular to the fiber orientation in the lower component 112.

Figs . 26 and 27 Hlustrate embedding sanitary tubing 114 or heating tubing 116 in DSP construction elements .

In Fig. 28, a fresh roHed plate cement-based DSP material is cut into bricks or tfles 120 by means of a grid-like cutter.

Figs . 29 - 31 Hlustrate a rolling method which may advantageously be used for forming the DSP-material 68 into plane or contoured board or panels 138. This is method, invented by the present inventor, is described in greater detaH in a Danish patent appH¬ cation filed on May 1 , 1981 in the name of Aktieselskabet Aalborg Portland- Cem en t-Fabrik, entitled "Valse og fremgangsmade til valsning af et deformerbart materiale" ("RoUer and method for rolling a defor able material") . Each roUer comprises a shaft 122 and a body member 128 made from a resilient material in which a number of rod-like members 124 of a stiff material are embedded so as to define a peripheral roUer surface 126 which is resistant to bending forces . The outer surface parts or edge portions 130 of the stiff members 124 may be exposed at the peripheral surface 126 of the roUer or covered by a thin covering layer, not shown.

A pair of spacer members 72 determining the thickness of the walls or ^" panels 138 to be formed, are arranged between a pair of roHers which are pressed together so as to flatten their peripheral surface part 132 of the roHers defining the nip therebetween . The roHers may have circular cyhdrical surfaces as shown in Fig. 29, or be provided with annular ridges 134 and annular grooves 138 for forming corrugated panels or waUs as Hlustrated in Figs . 30

^T EA-

and 31. One of the roUers in each pah* of roHers may also be provided with protrusions 140 for forming spaced holes 142 in the roHed product 138. These holes may, for example, be used for insertion of nails , screws , or other fastening means .

In Fig. 32, a reproduction casting of an archeologicaHy interesting rehef 144 placed under flowing water 30 is performed by surroun¬ ding the rehef 144 with a frame 146 and pouring DSP material into the frame through a hose 50. The DSP material reproduces the surface of the rehef to the last detaH, and due to its high internal coherence, is not dHuted or entrained by the flowing water.

In Fig. 33, a complete archeologicaHy interesting area 148 is re¬ produced by casting by means of DSP material, utilizing the strength of the DSP material (and optionaHy the possibility of incorporating reinforcing bodies) for obtaining a much larger cast than is possible with known materials for. this purpose .

Figs . 34 - 36 Hlustrate an advantageous method of molding an object from DSP material. This method, invented by the present inventor, is described in greater detaH in a Danish patent ap¬ pHcation filed on May 1, 1981 in the name of Aktieselskabet Aalborg Portland-Cement-Fabrik, entitled "Fremgangsmade og form til formning af en genstand i en formhulhed" ("Method and mold for shaping an article in a mold cavity") . The inner space of a molding container 156 comprising a cylindrical waH 158 with upper and lower flanges 160 and 162 and a bottom part or front piece 154 is divided into an outer mold cavity 164 and a central back-up space 166 by means of a flexible membrane 152 fastened to the container by clamping means 168 and 172. DSP-material ^* 24 may be introduced into the outer mold cavity through an opening 176 via a feeding line 178 by means of a pump 180. A back-up Hquid 182 is simultaneously introduced into the central space 166 through an opening 170 via a feeding line 184 by means of a pump 186. The central space 166 communicates with the atmosphere through an upper opening 174. The supply of DSP-material 24 and back-up Hquid to a mold cavity 164 and to the central space 166, respec¬ tively, is controUed by a control circuit 192 on the basis of

-g j EAlT

signal received from level sensors 188 so as to control the shape of the membrane 152 in a predetermined manner. AH* may escape from the mold cavity 164 through venting openings 194.

Fig. 34 Hlustrates how an extruder die may be molded by means of the molding method Hlustrated in Fig. 35. In this case, one end of the membrane 152 is fastened to spaced, oppositely arranged waH parts 150.

The molding container 196 shown in Fig. 36 is divided into two halves 198 and 200 having flanges 202 and 204 clamped together by means of bolts 206. A membrane 212 made from a non-elastic, deformable material divides the inner space of the molding con¬ tainer 196 into two mold cavities 208 and 210. DSP-material 24 is simultaneously fed into the mold cavities 208 and 210 through feed conduits 214, 216, and 218 by means a pump 220, and air may escape from the mold cavities through venting openings 222. This molding method permits simultaneous molding of a pair of objects having complementary shaped surface parts determined by the shape of the membrane.

Fig. 37 Hlustrates barrier effect when a large body or particle 221 close to a waH 223 impedes smaH particles 18 from entering into the narrow space between the large particle of diameter D and the waU. The size of the space not accessible to the particles 18 is designated f .

Fig. 41 Hlustrates a duct or cavity 244 which is being fiHed with DSP grouting 246 containing fibers 248.

Fig. 42 HHustrates a section of a long cavity fiHed with DSP paste 252 and DSP concrete 254. The filling has been performed in two steps, starting with the paste filling the entire volume and fol¬ lowed by injection with DSP concrete substituting the paste in the larger volume, but leaving the narrow fissueres or cavities 250 filled with the paste.

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Fig. 43 Hlustrates waU effect showing particles 258 adjacent to a waH 256. The particle concentration is lower in the narrow space adjacent to the waH than in the bulk. The thickness of the narrow space adjacent to the waH is approximately 1 particle diameter.

Figs . 44 and 45 Hlustrate the same procedure as Fig. 42. In Fig. 45, air 262 is entrained with the DSP paste and is thereby removed from the irregularities in the cavity waH, so that a perfect filling is obtained. In Fig. 46, the cavity is wetted with Hquid 264 which is introduced or present prior to the injection of the DSP paste and DSP concrete.

Fig. 47 Hlustrates the wetting of the surface of particles 266 by a Hquid 252 in Fig. 47 b as a result of treatment of the sohd surface, resulting in the creation of Hquid spreading, thus displacing the entrapped gas bubble 268.

Fig. 48 Hlustrates the sedimentation of rod-shaped particles 248 in a Hquid 250. Sedimentation from a Hquid with a low concentration of particles or fibers in the absence of surface forces results in a rather dense packing due to the fact that the fibers are aUowed to turn freely into horisontal position without interference with settling neighbouring particles .

Figs . 49 and 50 Hlustrate the injection og DSP paste and mortar into a cable duct 272 with a post-tensioning cable 270 by the two stage injection method according to the invention. The narrow spaces around the cable 270 are fHled with the DSP paste, whHe the bulk is filled with the DSP concrete 254. Figs . 51 and 52 Hlustrate spacers 274 which may be used to keep the space arount the cable- 270 more accessible to a coarser injection.

Figs-. 53 and 54 Hlustrate the opening of a crack in fluid-fiUed particle materials . An ultrafine crack 276 passes through an ultrafine particle system 14 which is situated in the voids between larger particles 12 (typicaHy particles B) . In magnification is shown, at 278, water between the maU particles . In Fig. 54, a broader crack 276 passes through a cement system (particles B

- RE

(12) containing a dHute slurry with ultrafine particles 14 in the voids . Stabilizing Hquid-gas interphases are formed.

Fig. 55 Hlustrates extrusion of a fiber-supported DSP sheet 280 having tongue-and groove-like edges 282 and 284 and the winding of the sheet on a tube 286 to form a coating 288.

Fig. 56 Hlustrates the appHcation of an internal layer 24 of DSP material in a pipe 290 by means of a plastic tube 292 which shapes the surface of the DSP coating.

Figs . 57 - 62 Hlustrate preparation of Hghtweight foam having strong through-going waUs of DSP material based on the pressure release shaping of compressibe Hghtweight bodies in a Hquid phase, such as discussed in detaH Hi the section "HIGH QUALITY

FOAM" . In Figs . 57 - 59, hoHow bodies such as polystyrene spheres in a Hquid, e.g. a DSP fluid, or a suspension of particles A, are compressed by moving a piston 294, thus increasing the pressure. In Fig. 60, the surplus of Hquid is drained off . In Fig. 61, the pressure is released (and optionaHy replaced with vacuum conditions) by moving . back the piston after the Hquid transport has been stopped (the draining openings have been closed) , and the hoHow bodies expand and generate a dense regular, controUed structure with narrow "waUs" of Hquid phase therebetween, such as is Hlustrated in enlarged scale in Fig. 62.

Figs . 63 and 64 Hlustrate controUed placing of Hghtweight particles or bodies 302 and fibers 22 introduced through tubes 300, 304, and 306, respectively, to form advanced foam type materials .

Figs . 65 and 66 Hlustrate the generation of densely packed pores by tensioning elastic bodies 310 arranged in a containing 308 con¬ taining a suspension 24 of particles and thereafter releasing the tension .

Fig. 67 Hlustrates winding of elastic material 316 submerged in a slurry of densely packed particles by rotation around an axis 314.

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Fig. 68 Hlustrate the incorporation of specific particles 320 in the particle A structure in a DSP material.

Fig. 69 Illustrates the maximum size of large towers designed to

5 carry their own weight only. Material properties are as indicated in Table A in the section "LARGE STRUCTURES", factor of safety

2.5. The diameter of the top of the tower is 200 m, and the slope at the bottom is 1 : 1.

The shape of the towers is given by 0 L = L In ^d c

^C ST where L is the hight, L is a critical length, and d and d are the diameter at the height L and at the bottom, (d = 2L ) 2σ 1 c c

(L = — . - , where the factor of safety f = 2.5) .

^C Pg f 5

Figs . 70 and 71 have been discussed in the section "LARGE

STRUCTURES".

Fig. 72 Hlustrates large bridges of maximum size and identical 0 shape made from DSP with refractory grade bauxite (326) and high quaHty concrete (328) .

Fig. 73 is a diagram Ulustrating the strength/density ratio for large bending members designed to carry their own weight only 5 and showing the maximum span as a function of the stress-density ratio.

Fig. 74 Illustrates large bending members designed to carry their own weight only, representing situations in which increased 0 strength- density ratio .is utilized to reduce the thickness of the members , but keeping the span constant (H) .

Fig. 75 shows prismatic bending members with rectangular cross section and H-shaped cross section , respectively. The arc of a c circle K _* defines the maximum radius of curvature R.

Fig. 76 shows half of a bridge span with an arc of a circle Re ^¬ defining the maximum radius of curvature.

_/ - TREX

Aspects of the invention are defined in the appended claims.

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