Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
SHAPED ARTICLE AND COMPOSITE MATERIAL AND METHOD FOR PRODUCING SAME
Document Type and Number:
WIPO Patent Application WO/1980/000959
Kind Code:
A1
Abstract:
Shaped articles with a coherent matrix which comprises homogeneously arranged inorganic solid particles (A) of a size of from about 50 66 to about 0.5 micron, such as silica dust particles, and densely packed solid particles (B) having a size of the order of 0.5 - 100 micron and being at least one order of magnitude larger than the respective particles A, such as Portland cement particles, the particles A being homogeneously distributed, especially densely packed, in the void volume between the particles, B, are made from an easily flowable composite material containing a very low amount of liquid and an extremely high amount of a dispersing agent, such as a concrete superplasticiser. Test specimens with Portland cement-silica dust-based matrices with dense packing of the silica dust have higher compressive strengths than hitherto reported, and reinforcements such as fibers or steel bars are subject to a high degree of fixation in the dense Portland cement-silica dust matrix because of the density of the matrix contacting the reinforcement such as illustrated in Fig. 5 which shows a plastic fiber incorporated in the dense matrix. Composite material for making shaped article comprises dispersing agent in sufficiently high amount to obtain a viscous to plastic consistency of the composite material with the small volume of liquid necessary to fill voids between particles A and B. The shaping of the composite material may be performed in a low stress field and without exchange of liquid with the surroundings.

Inventors:
BACHE H (DK)
Application Number:
PCT/DK1979/000047
Publication Date:
May 15, 1980
Filing Date:
November 02, 1979
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ALLBORG PORTLAND CEMENT (DK)
BACHE H (DK)
International Classes:
B28B1/08; B28B23/00; C04B24/22; C04B20/00; C04B28/04; C04B; (IPC1-7): C04B13/21; C04B15/00; C04B31/00
Foreign References:
US4111711A1978-09-05
US3957520A1976-05-18
CH300853A1954-08-31
US3754954A1973-08-28
DE2510224A11975-09-25
US3489582A1970-01-13
AT312490B1974-01-10
FR2229662A11974-12-13
US4118242A1978-10-03
Download PDF:
Claims:
Claims .
1. A shaped article comprising a coherent matrix, the matrix comprising A) homogeneously arranged inorganic solid particles of a siz of from about 50 A to about 0.5 μ, or a coherent structur formed from such homogeneously arranged particles , an B) densely packed solid particles having a size of the orde of 0.5 100 μ and being at least one order of magnitud larger than the respective particles stated under A) , or 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 correspondin to the one obtainable by gentle mechanical influence on system of geometrically equally shaped large particles in whic locking surface forces do not have any significant effect, and optionaEy C) additional bodies which have at least one dimension whic is at least one order of magnitude larger than the particles A, whereby, when the shaped article is not selected from the group consisting of in situ cast oil well walls ; duct fillings ; fissur fillings ; sheets ; panels and tiles of thinwalled plane or corrugate shape; anticorrosion protecting covers applied on steel and con¬ crete members ; pipes ; tubes ; electrically insulating members : nuclear shieldings ; and containers ; the following provisos apply : 1) when additional bodies C are not present or are present and consist of sand and/or stone, at least 20% by weight of the par tides B are Portland cement, and further, 2) when the particles B do not have a molecular structure different from the molecular structure of the particles A, the shaped article is selected from the group consisting of articles produced by—shaping in a low stress field of less than 5 kg/cm 2 , preferably less than 100 g/cm 2 , articles having at least one dimension of at least one meter and .
2. having a minimum cross section of at least 0.1 m , and articles having a complex shape that does not permit its establishment by powder compaction.
3. 2 A shaped article as claimed in claim 1 in which the particles A are densely packed, or the coherent unitary structure A is formed from such densely packed particles .
4. A shaped article as claimed in claim 1 or 2 in which the matrix comprises a dispersing agent.
5. A shaped article as claimed in any of claims 1 3 in which part of the particles B are inherently weak particles of such strength and rigidity that they would be deformed or crushed to a substan 2 tial extent under stresses larger than 5 kg/cm applied to a powder mass consisting of the particles , which particles have retained their geometric identity during the shaping process .
6. 5 A shaped article as claimed in any of of the preceding claims in which the particles A are inherently weak particles of such strength and rigidity that they would be deformed or crushed to a substan 2 tial extent under stresses larger than 5 kg/ cm applied to a powder mass consisting of the particles , which particles have retained their geometric identity during the shaping process .
7. A shaped article as claimed in any of the preceding claims which contains additional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A, said additional bodies being bodies of a solid, a gas , or a liquid. OMPI IPO .
8. A shaped article as claimed in claim 6 in which the additiona bodies are selected from the group consisting of compactshape bodies, plateshaped bodies , and elongated bodies .
9. 5 8.
10. A shaped article as claimed in claim 6 or 7 in which the additi¬ onal bodies are selected from the group consisting of sand, stone, polystyrene bodies, including polystyrene spheres , expanded clay, hollow glass bodies, including hollow glass spheres , expande shale, natural lightweight aggregate, gas bubbles, metal bars , 10 including steel bars , fibers , including metal fibers such as stee fibers , plastic fibers , Kevlar fibers, glass fibers , asbestos fibers , cellulose fibers, mineral fibers, high temperature fibers, whiskers, including inorganic nonmetallic whiskers such as graphite an Al?O„ whiskers and metallic whiskers such as iron whiskers , heav 15 weight components , and hydrogenrich components .
11. A shaped article according to any of claims 6 8 in which the additional bodies are inherently weak solid bodies of such strength and rigidity that they would be deformed or crushed to a substan 2 20 tial extent under stresses larger than 5 kg/cm applied to a pow¬ der mass consisting of the particles, which particles have retaine their geometric identity during the shaping process .
12. A shaped article as claimed in any of claims 6 9 in which th 25 additional bodies are densely packed.
13. A shaped article as claimed in any of the preceding claims i which the particles B are particles which cure by partial dissolutio in a liquid, chemical reaction in the dissolved phase, and precipi 30 tation of a reaction product.
14. A shaped article as claimed in any of the preceding claims in which the particles A are particles which cure by partial dissolutio in a liquid, chemical reaction in the solution, and precipitation of 35 reaction product. fθRE OMP IP .
15. A shaped article as claimed in claims 11 and 12 in which the particles A show a substantially lower reactivity than the particles B , o substantially no reactivity.
16. A shaped article according to any of the preceding claims in . which the^particles B comprise. at .leas. ~=SQ%~ by weight of Portland cement particles .
17. A shaped article as claimed in claim 14 in which the particles B comprise particles selected from fine sand, fly ash and fine chalk .
18. A shaped article as claimed in any of the preceding claims in which the particles A are particles of silica dust having a specific 2 surface area of about 50, 000 2, 000,000 cm /g, in particular about 250,000 cm2/g.
19. 17 A shaped article according to claim 16 in which the silica dust particles are 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 particles A + B .
20. A shaped article as claimed in any of the preceding claims which contains sand and stone as additional bodies .
21. A shaped article as claimed in any of the preceding claims which contain fibers as additional bodies .
22. A shaped article as claimed in claim 19 in which the fibers are selected from the group consisting of metal fibers , including steel fibers, mineral fibers , glass fibers, asbestos fibers, high tempera¬ ture fibers , carbon fibers , and organic fibers, including plastic fibers .
23. A shaped article as claimed in claim 20 in which the fibers are chopped fibers , or continuous fibers or yarns or ropes , or rovings or staple fibers , or fiber nets or webs .
24. A shaped article as claimed in claim 21 in which the fibers ar polyolefin fibers, preferably polypropylene fibers .
25. A shaped article as claimed in any of the preceding claim which additionally contains reinforcing steel as bars or rods .
26. A shaped article as claimed in any of claims 21 23 in whic the bars, rods, or fibers are prestressed.
27. A shaped article as claimed in any of claims 19 24 in whic the matrix as defined in any of the preceding claims constitute only part of the total binder matrix of the article and is mainly ar¬ ranged around reinforcing fibers or bars in the article.
28. A shaped article as claimed in claim 25 in which the matrix as defined in any of the preceding claims is a matrix of cured grout¬ ing mortar in post tension concrete .
29. An article as claimed in any of claims 21 23 in which the ad ditional bodies (fibers, bars , or rods) have retained their geome¬ tric identity during the shaping process .
30. An article as claimed in any one or more of the precedin claims , which article is a sheet or panel of thinwalled plane o corrugated shape; a pipe; a tube; a refractory lining or a refrac tory lining component; a . protecting cover such as a protectin cover applied on steel, ordinary concrete, masonry, pavements an roads ; a roofing material such as a roofing panel or tile; an elec tricallyinsulating member; a nuclear shielding; a seafloor struc ture for deep water applications ; a container; an in situ cast oi well wall; or a loadbearing member in structural engineering suc as a beam, a shell, a column, typically as reinforced concrete", especially as prestressed concrete.
31. An article as claimed in claim 28 in which the matrix thereof i fiber reinforced.
32. An article as claimed in claim 29 in which the reinforcing fibers are polypropylene fibers have a tensile strength of at least 4000 kp/cm 2 , a modulus o elasticity of at least 7 x 104 kg/cm 2 , and an elongation at rupture of at the most 8 percent.'.
33. A compositematerial or producing* a shaped article, comprising A) inorganic particles of a size of from about 50 A to about 0.5 μ , and 0 B) solid particles 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) , 5 a liquid, and a surface active dispersing agent, the amount of particles B substantially corresponding to dense 0 packing thereof in the composite material with homogeneously packed particles A in the voids between particles B , the amount of liquid substantially corresponding to the amount necessary to fill out the voids between particles A and B , and the amount of dispersing agent being sufficient to impart to the composite material a fluid to 5 plastic consistency in a low stress field of less than 5 kg/cm 2. , 2 preferably less than 100 g/cm , and optionally 0 c) additional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A) , with the proviso that when additional bodies C are not present or are present and consist of sand and/or stone, at least 20% by 5 weight of the particles B are Portland cement particles . OMPI 32 A composite . material for producing a shaped article, comprisin A) inorganic particles of a size of from about 50 A to abou 0.5 μ, B) solid particles 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) , and a surfaceactive dispersing agent, the amount of particles B substantially corresponding to dens packing thereof in the composite material with homogeneously pack particles A in the voids between particles B , and the amount o dispersing agent being sufficient to impart to the composite materi a fluid to plastic consistency in a low stress field of less than kg/cm 2 , preferably less than 100 g/cm 2 , when an amount of liqui substantially corresponding to the amount necessary to fill out th voids between particles A and B has been added, and optionally C) additional bodies which have at least one dimension whic is at least one order of magnitude larger than the particles A with the proviso that when additional bodies C are not present o are present and consist of sand and/or stone, at least 20% b weight of the particles B are Portland cement particles .
34. A composite material as claimed in claim 31 or 32 in which th particles . A are present .in a volume substantially corresponding t dense packing to fill the voids between the particles B when den sely packed, and the surface active dispersing agent is present i an amount sufficient to allow dense packing of the particles A in 2 low ssttress field of less than 5 kg/cm , preferably less than .10 g/cm 2 .
35. A composite material as claimed in claim 31, 32 or 33 in which the dispersing agent is present in an amount which substantially corresponds to the amount whic wiH fully occupy the surface of the particles A. 35~ composite material as claimed . in— any— of claims 31 — 34 in which the particles A are silica dust particles having a specific 2 surface area of about 50,000 2,000,000 cm /g, in particular about 2 250,000 cm /g, the particles B comprise at least 50% by weight of Portland cement, and the dispersing agent is a concrete superplas¬ ticiser.
36. 36 A composite material as claimed in claim 35 in which the par¬ ticles B comprise particles selected from fine sand, fly ash, and fine chalk.
37. A composite material as claimed in claim 35 or 36 in which the concrete superplasticiser is an alkali or alkaline earth metal salt of a highly condensed naphthalene sulphonic acid/formaldehyde con densate, of which typically more than 70 percent consist of mole¬ cules containing 7 or more naphthalene nuclei.
38. A composite material as claimed in claim 37 in which the alkali or alkaline earth metal salt is a sodium or calcium salt.
39. A composite material as claimed in claim 37 or 38 in which the amount of the superplasticiser dry matter is in the range of 1 4, in particular 2 4, percent, calculated on the total weight of the Portland cement and the silica dust.
40. A composite material as claimed in any of claims 37 39 in which the liquid is water to a weight ratio between water and Portland cement and any other particles B plus silica dust of 0. 12 to 0.30 , preferably 0. 12 to 0.20.
41. A process for preparing a shaped article according to any of the preceding claims , comprising combining OMPI A) inorganic solid particles of a size of from about 50 A to about 0.5 μ, and B) solid particles having a size of the order of 0.5 100 μ 5 and being at least one order of magnitude larger than the respective particles stated under A) , a liquid, 10 and a surface active dispersing agent, the amount of particles B substantially corresponding to dense packing thereof in the composite material with homogeneously packe particles A in the voids between particles B , the amount of liquid 15 substantially corresponding to the amount necessary to fill out 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 , 20 and mechanically mixing the above ingredients , optionally together with additional bodies which have at least one dimension which is one order of magnitude larger than the particles A until a viscous to plastic mass comprising the particles A and optionally other par 25 tides , has been obtained, and thereafter, if desired, combining the resulting mass with ad¬ ditional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A by mechanical 30 means to obtain the desired distribution of such additional bodies , and finally casting the resulting mass in the desired shape in a stress field, optionally with incorporation of additional bodies which have at least one dimension which is at least one order of magnitud larger than the particles A during the casting, 35 with the proviso that when additional bodies are not present or are present and consist of sand or stone, the particles B comprise at least 20% by weight of Portland cement particles . /j*. W W 42 A process as claimed in claim 41 in which the stress field re¬ sponsible for the shaping of the mass is mainly due to gravity forces acting on the mass , or forces of inertia acting on the mass , or contact forces , ■ ■ . . .. .. . ■ or the simultaneous acting of two or more of the above forces .
42. A process as claimed in claim 41 in which the stress fiel mainly responsible for the shaping of the mass is due to oscillating forces with a frequency between 0.1 Hz and 10 Hz, the oscillating forces being of the type stated in claim 42, or due to a combination of such oscillating forces with nonoscillating forces of the type stated in claim 42.
43. A process as claimed in claim 41 in which the article is shaped 2 by extrusion or rolling at a shaping pressure of up to 100 kg/cm .
44. 45 A process as claimed in claim 41 in which the article is shaped by spraying, painting or brushing, injection or application of a layer of the mass on a surface and conforming the mass to the shape of the surface .
45. A process as claimed in claim 40 in which the article is shaped by centrifugal casting.
46. A process as claimed in claim 41 in which the mass , as a cohe¬ rent mass , is poured into a liquid where it displaces part of the liquid and arranges itself as a coherent mass .
47. A method as claimed in claim 47 in which the liquid is water, and the mass is paste, mortar, or concrete for building an under¬ water structure .
48. Shaped articles whenever produced by the process claimed in any of claims 40 47.
49. Shaped articles whenever produced from the composite materia claimed in any of claims 31 40.
50. A shaped article as claimed in any of claims 1 30 and 49 5 in which at least part of the matrix comprises an additional soli substance in the voids of the structure formed from the particles and B .
51. A shaped article as claimed in claim 51 in which the additiona solid substance is selected from the group consisting of organi polymers such as polymethylmethacrylate or polystyrene, low melting metals , and inorganic metalloid solids such as sulfur.
52. A shaped article as claimed in claim 51 or 52 in which at leas the part of the matrix adjacent to exterior surfaces of the articl comprises the additional solid substance in the voids of the struc ture formed from the particles A and B .
53. A method for preparing a shaped article as claimed in any o claims 51 53, comprising partially or completely infiltrating shaped article as claimed in any of claims 1 30 and 49 50 wit a liquid and thereafter solidifying the liquid.
54. A method as claimed in claim 54, comprising performing th infiltration with a liquid which shows at least one of the followin characteristics : it is capable of wetting the internal surface of the structur formed from the particles A and B , it contains molecules of a size which is at least one order o magnitude smaller than the particles A, on solidification by cooling or polymerisation, it leaves a soli substance of substantially the same volume as the liquid and thereafter solidifying the liquid by cooling or polymerisation .
55. A process as claimed in claim 54 or 55 in which the efficiency of the infiltration with the liquid is enhanced by one or more of the following measures : drying the article or the part thereof to be impregnated, applying vacuum on the article or the part thereof to be infiltrated prior to the infiltration treatment, applying external pressure to the infiltrating liquid after con¬ tacting the article with the infiltrating liquid.
56. The use of a composite material comprising A) inorganic particles of a size of from about 50 A to about 0.5 μ , B) solid particles 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) , a liquid, and a surface active dispersing agent, the amount of particles B substantially corresponding to dense packing thereof in the composite material with homogeneously packed particles A in the voids between particles B , the amount of liquid substantially corresponding to the amount necessary to fill out 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 , OMPI and optionally C) additional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A, for producing shaped articles selected from the group consisting of in situ cast oil well walls; duct fillings ; fissure fillings; sheets ; panels and tiles of thin walled plane or corrugated shape; corro¬ sionprotecting covers applied on steel and concrete members; pipes ; tubes ; electrically insulating members : nuclear shieldings; and containers .
57. 58 A process for preparing a shaped article selected from the group consisting of in situ cast oil well walls; duct fillings ; fissure finings ; sheets ; panels and tiles of thinwalled plane or corrugated shape; corrosion protecting covers applied on steel and concrete members ; pipes ; tubes ; electrically insulating members : nuclear shieldings ; and containers ; comprising combining A) inorganic solid particles of a size of from about 50 A to about 0.5 μ , and ' B) solid particles 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 liquid, and a surfaceactive dispersing agent, the amount of particles B substantially corresponding to dense packing thereof in the composite material with homogeneously packe particles A in the voids between particles B , the amount of liquid substantially corresponding to the amount necessary to fill out 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 , and mechanically mixing the above ingredients , optionally together with additional bodies which have at least one dimension which is one order ofmagnitude larger* than ~the particles A until a viscous ' to plastic mass comprising the particles A and optionally other par tides , has been obtained, and thereafter, if desired, combining the resulting mass with ad¬ ditional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A by mechanical means to obtain the desired distribution of such additional bodies, and finally casting the resulting mass in the desired shape in a stress field, optionally with incorporation of additional bodies which have at least one dimension which is at least one order of magnitude larger than the particles A during the casting.
58. 59 A shaped article comprising a matrix which comprises a Portland cementbased binder and optionally added inorganic bodies of com¬ pact shape such as sand or stone, the article having a compressive strength of more than MPa, measured, on a test specimen having a diameter of 10 cm and a height of 20 cm, when the matrix is a concrete, as defined by the largest of the compact shaped bodies being larger than 4 mm, MPa, measured on a test specimen having a diameter of 3 cm and a height of 6 cm, when the matrix is a mortar, as defined by the largest of the additional compactshaped bodies being between 4 mm and 0. 1 mm, MPa, measured on a test specimen having a diameter of 1 cm and a height of 2 cm, when the matrix is a paste, defined by the largest of the additional compactshaped bodies being smaller than 0.1 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 , REAyf° OMPI and/or has a complex shape which does not permit its establishment by powder compaction .
Description:
Shaped Article and Composite Material and Method for Producing same.

The properties of materials having a coherent structure comprising fine solid particles or a coherent structure formed from such par¬ ticles are mostly" strongly dependent on- the -particle size and upon how densely and homogeneously the particles are packed. With increasing density and decreasing particle size, the mechanical strength, the resistance to chemical attacks , the frost resistance, and the hardness increase. The mechanical strength increases with increasing density and with decreasing particle size. However, in the shaping of an article by deformation of a powder mass, the finer the powder -is , the more difficult is it to work with a high particle concentration, - because surface forces preventing that the particles slide relatively to each other, become the more important, the finer the powder is . This is especially pronounced for aqueous suspensions of Portland cement where, the dissolved salts make it difficult to eliminate the surface forces . Therefore, it is normally not easy to arrange Portland cement particles in water in dense packing when the Portland cement particles are too .fine.

For example, in binders based on Portland cement, the powder fineness has become established with a specific surface about 3000 - 5000 cm /g (in rare cases up to 6000 cm 2 /g) , and the powder concentration in the aqueous suspension normally corre¬ sponds to a water/cement weight ratio of 0.7 - 0.4 (for very strong concrete down to 0.3) . Cement which is substantially finer - and which should theoretically give better properties - is difficult to mix and cast, especially in pastes with high cement concentra- tion, and very dense pastes (low water/cement-ratio) based on very coarse cements are not "attractive because " of the coarse structure and slow hydration .

One of the main aspects of the present invention is to improve powder-based binders (especially binders based on Portland ce¬ ment) by adding powders which are one or more orders of size finer than the binder powder (to form basis for a homogeneous and

OMPI

dense particle packing and an extremely finely porous structure and secure a very homogeneous particle arrangement and a hig particle concentration (low water/cement-ratio) by adding larg amounts of surface active dispersing agents . 5

This makes it possible, inter alia, to obtain binders which are con siderably stronger, much denser, more durable and especially fa better suitable for fixation of reinforcing bodies such as fibers an bars than the unmodified binders . Also, it becomes possible t 10 shape articles comprising such binder matrices in a low stress fiel and without any exchange of material with the surroundings, suc as appears from the explanation given below.

In a very brief form, some basic principles of this invention coul 15 be said to be contained in the below four points :

1. The invention utilizes known particle geometry strategy on fin • - particle systems which are 1 - 2 orders of magnitude (powers o

10) finer than the Portland cement-containing particle systems i 20 which it has so far been possible to utilize the principles . In ac cordance with the invention,- these principles are in particula used on aqueous suspensions of Portland cement and ultrafin particles which are 1 to 2 orders of magnitude smaller than th cement particles .

25

2. This has been obtained by a dosage of dispersing agents (1 - by weight of a concrete superplasticiser dry matter calculated o the cement plus ultrafine particles) which is .up to one order o magnitude higher than in the known art.

30

3. In the material of the invention, strength and durability ar greatly increased. In addition to this, mechanical fixation of re inforcing bodies , e . g. fine incorporated fibers , is increased eve more than the strength, the increase being one or several order 35 of magnitude. This is due to the fact that the dimensions of roug ness and wave configuration on the reinforcing bodies which ar necessary for obtaining "mechanical locking" of the. reinforcin

bodies in the matrix, are lowered by 1 - 2- orders of magnitude . This opens up the possibility of "mechanical locking" of fibers which are one to two orders- of magnitude finer than hitherto .

4. The materials according to the invention may be shaped from a mass- with.. -plastic -to. law viscous—consistency .-by--simple.- shear . de- formation without any exchange of material with the surroundings , 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 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 invention also opens up the possibility of new and more advantageous pro¬ duction techniques for known articles .

«

Hence, the invention is based upon the discovery of the possibility of obtaining dense or homogeneous packing in these extremely small particle systems, in particular in a "gentle" way in contrast to the known art high pressure powder compaction techniques which, for Portland cement-based systems, constituted the only possible methods of obtaining such structures , and this opens up a wide range of novel products and processes within not only the cement field, but also many other related or unrelated fields such as ceramics and powder metallurgy.

Novel products which have become obtainable through the present invention may be defined as shaped articles comprising a coherent matrix,

the matrix comprising

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

B) densely packed solid particles having a size of the orde of 0.5 - 100 μ and being at least one order of magnitud larger than the respective particles stated under A) , or coherent structure formed from such densely packed par ticles ,

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

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

and optionally

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

with certain provisos which will be explained below.

Throughout this specification, the term "particles A" designate inorganic solid particles of a size of from about 50 A to abou 0.5 μ, and the term "particles B" designates solid particles havin a size of the order of 0.5 - 100 μ and being at least one order o magnitude larger than the respective particles A. The term "shape article" designates any shaped structure comprising a matrix a defined above and includes such special kinds of articles as , e.g. road surface layers , fissure fillings , coatings on tubes , etc. which may not always be associated with the term "article" .

Dense packing dominated by the geometry of the particles (withou influence from surface forces) has been treated worldwide in th literature dealing with particulate technology in various fields , fo example in "Particulate Technology, Clyde Orr, Jr. 1966, Th

/ j* .

MacMiϋan -Company, New York, and "Principles of Particulate Mechanics" , Brown and Richards , 1970, Pergamon Press . It is characteristic that packing of particle • systems in which surface 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) irrespective 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 com¬ paction 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 . (Even such dense packing is not completely ideal; ideality would necessitate individual placing of each particle. )

The substantially coherent structure of the matrix of the above- defined articles of the invention may be due to the homogeneously

arranged or densely packed particles A being combined with ea other to form a coherent structure, or due to solid particles B stated above being combined with each other to form a substantia coherent structure, or both the ultra fine particles A and the pa tides B in the shaped articles may each be combined with ea other to form coherent structures , and/or particles A being co bined with particles B to form the coherent structure. The co bination between the particles A or between the particles B between particles A and/or particles B may be of any charact which results in a coherent structure . In systems comprising c ment particles as particles B and silica dust particles (as defin below) as particles A the coherent structure is " formed due partial dissolution of the solid particles in the aqueous suspensi from which the articles are made, chemical reaction in the solutio and precipitation of the reaction product, the silica dust being le reactive in this regard than the cement. In this connection it noted that dependent on the identity of the particles A and also other mechanisms imparting coherence may have been respo sible for the coherence -of the matrix, such as melting or sinte ing, etc . The chemical reaction mentioned above may be one whi takes place between the particles A or their dissolved constituent or between the particles B or their dissolved constituents , between particles A and B or between constituents of particles and particles B .

Shaped articles comprising a matrix having a substantially cohere structure comprising homogeneously arranged or densely pack particles A together with densely packed particles of Portla cement were obtainable in the known art only by compaction in high stress field, typically by high pressure powder compactio

Hence, one completely novel class of shaped articles of the inve tion comprises shaped articles produced by shaping in a low stre field of less than 5 kg/cm 2 , preferably less than 100 g/cm 2 , a having a matrix of a substantially coherent structure comprisi homogeneously arranged or densely packed particles A or a coh rent structure formed from such homogeneously arranged or de sely packed particles A, and densely packed particles B , at lea

τ S.

20% by weight of the densely packed particles B being Portland cement particles , or a coherent structure formed from such densely

- packed- -particles B . Another way of -definin the- novel class of

- shaped articles of the invention with 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 present invention, by high pressure powder compaction technique . Another way of expressing this kind of novel article which was only made possible through the present invention is by. defining that the articles have a complex shape that does not permit its establishment through powder compaction. Finally, when the par¬ ticles 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 are completely novel irrespective of the size or shape thereof . While it may have been possible in powder compaction techniques to obtain a combination of the two systems comprising homogeneously ar¬ ranged or densely packed particles A and densely packed par¬ ticles 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 this invention is that it is possible to establish structures of the types discussed above with inhe¬ rently 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 opens up the possibility of establishing dense structures with materials not previously available therefor.

OMPI _

In most cases , the most valuable strength properties are obtainabl when both particles A and particles B are densely packed. Thi situation is illustrated in Fig. 1 which shows the principles of th geometrical arrangement involving dense packing in fresh past consisting of Portland cement particles and ultra fine particle between the Portland cement particles . With reference to test made with mortar, fiber- reinforced paste and concrete based o this novel matrix, the Portland cement particles (average dimensio 10 μ) were arranged in a dense packing corresponding to a volum fraction of cement (volume of Portland, cement divided by tota volume) of 0.43 - 0.52. If ordinary cement paste - not containin ultra fine particles - had been arranged in the same dense packin it would correspond to a water/cement weight ratio of 0.42 to 0.30. This would normally be claimed to be densely packed. In the ne material according to the invention, it has been found possible t incorporate further up to 50% by volume of ultra fine solid par ticles in voids between the cement particles . The solid incorporate was fairly densely packed extremely fine spherical silica particle with an average diameter of 0.1 μ and a specific surface of abou 2 250,000 cm /g. The total volume fraction of solid in the matrix o 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 silic dust particles depends on the grain size distribution of the silic dust and, to a large extent, on the void available between th densely packed particles B . Thus , a well-graded Portland cemen containing additionally 30% of fine spherically shaped fly ash par ticles will leave a much smaller available void for the silica dus when densely packed than correspondingly densely packed cemen in which the grains are of equal size. In systems in which th particles B are mainly Portland cement, dense packing of silic dust would most likely correspond to silica dust volumes from -1 to 50% by volume of particles A + particles B . Similar considera tions apply to systems comprising other types of particles A and B

In the following specification and claims , the terms "ultra fine silica particles" or "silica dust" are intended to designate SiO -rich

2

- particles- having- a -specific surface of- about 50,000 - 2,000,000 cm /g,

2 especially about 250, 000 cm /g. Such a product is produced as a by-product in the production of silicium metal in electrical furnaces

- an -comprises particles in a par-tiele-size-range- fro -about 50 A to about 0.5 μ , typically in the range from about 200 A to about

0.5 μ .

The aspect of the invention involving dense packing of extremely fine powders has , for example, been realized in concrete (Example

1) , mortar (Examples 3 and 9) , and thin extruded panels with a reinforcement of plastic fibers (Example 2) . In all of these cases , the binder matrix was prepared from Portland cement (specific surface about 2400 - 4400 pm /g) and ultra fine spherical silica dust (specific surface 250,000 cm 2 /g) arranged in an extremely dense packing (water/powder weight ratio 0.18 and 0. 13, respecti¬ vely) by using, as dispersing agent, a concrete superplasticizer in an extremely high amount (1 - 4% by weight, in particular 2 - 3% by weight, of superplasticiser 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 cy- lindrical 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 superplasticising additives (vide Example 1) . The compressive strength of mortar prepared from an easily flow¬ able 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 accordance with this , Portland cement-based articles of the present invention can also be defined by referring to the uniquely increased compressive strength of their matrix in comparison with

CMPI-=.

known art. Expressed in this way, by means of compressiv strength values which are reasonable in view of the experiment reported in the Examples , the invention relates to a shaped articl comprising a matrix which comprises a Portland cement-based- bind and optionally added inorganic bodies of compact shape such a sand or stone, the matrix having a compressive strength of mor than

130 MPa, measured on a test specimen having a diameter o 10 cm and a height of 20 cm, when the matrix is a concrete as defined by the largest of the compact-shaped bodies being larger than 4 mm,

150 MPa, measured on a test specimen having a diameter o 3 cm and a height of 6 cm, when the matrix is a mortar as defined by the largest of the additional compact- shape bodies being between 4 mm and 0.1 mm,

200 MPa, measured on a test specimen having a diameter of 1 cm and a height of 2 cm, when the matrix is a p'aste defined by the largest of- the additional compact-shaped bodie being smaller than 0.1 mm,

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

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 establishmen by powder compaction.

The production of a dense material where part of the particles are weak particles retaining their geometric identity during th shaping process , rendered possible through the present invention is of particular interest, for example, in the case where part o particles B consist of uncrushed fly ash from power plants , a such particles have a beneficial spherical shape; fly ash contains substantial amount of weak hollow particles of the spherical shap which gives desirable flow properties of the casting mass , bu

which are likely to be crushed in traditional high pressure com¬ paction . Mortar fabricated with gentle shaping according to the - present invention -and containing - Portland cement, spherical power plant fly ash particles and ' silica dust is illustrated in Example 9. The compressive strength of the fly ash mortar was as high as 160

MPa. . . . .._ . .

Example 2 illustrates the production of plastic fiber-reinforced panels with the novel matrix. These panels showed an astonishing' behaviour, in that, apart from being very strong (bending strength in tension about 25 MPa) , they showed toughness which is a highly desirable property . The toughness is especially astonishing in view of the fact that the fibers were very short (6 mm polypropylene fibers) and the amount of fiber was moderate (2% by weight) . That the very strong binder which is brittle per se was made tough with the above-mentioned reinforcement indicates that the material of the invention gives at least one order of magnitude better fixa¬ tion of fine plastic fibers than ordinary cement matrices, and scan¬ ning electron microscopy -investigations makes it likely that the new. material behaves in this manner, as the new material appears ex¬ tremely dense even at very 'high degrees of magnification. This appears from Fig. 5 which is a drawing made on the basis of a scanning electron microscopy photograph of a 30 μ thick polypro¬ pylene fiber anchored in a cement- silica matrix of the invention (vide Example 2) . It will be noted that the matrix is extremely dense compared with ordinary cement matrices and is tightly packed against the fiber surface.

Hence, the very dense matrix obtainable with Portland cement and the ultra fine silica particles in dense packing shows unique capa¬ bility of fixing fine fibers (fibers of cross-sectional dimensions of say, less than 50 μ) , as it permits the establishment of a local wedging effect which is not present in ordinary cement paste, ordinary cement paste having a rather open structure in icrosco- pic scale .

The novel matrix also gives a considerably better fixation of coar ser reinforcement, e.g. of steel in steel-reinforced concrete. Thi is illustrated in Example 10 in which the resistance to drawin ou very smooth 6 mm - steel bars cast into cement- silica mortar to depth of 60 mm was 70% of the yield stress of the steel and th pull out work was 8 - 10 times the corresponding pull out work i a reference mortar having a compressive strength (38 MPa) o about one fourth to one fifth of the compressive strength of th mortar of the invention (179 MPa) . Thus, in this experiment, th work of pulling out the smooth steel bars is increased relativel more than the compressive strength.

This opens up new aspects in the field of steel- reinforced concret which will be discussed in greater detail below.

Dense packing of similar fine particle systems was known, fo example in connection with colloidal silica used, for example, fo coatings . It was also know to obtain very dense materials usin such ultra fine materials- together with materials of a fineness cor responding to Portland cement, but with a more favourable collo idal-physical behavior than Portland cement. Thus , it was know from British Patent No. 1,320, 733, to produce hydraulic settin refractory compositions comprising hydraulic aluminous cement plu fine particles having a particle size less than 1 micron shaped b use of deflocculating agents to obtain good quality refractory com positions . These compositions were prepared using a relativel high ratio of water to cement plus fine powder (0.7 - 1.0) , an the strength of the material prior to heating to 1350 - 1600°C wa not particularly improved, the strength level obtained, 40 MPa being low compared to the strength obtained according to the prin

- ciples of the present invention. It was also known to produce suc aluminous cement and MgO-based refractory compositions , but wit much higher strength, by combining particles of aluminate cemen and ultra fine particles arranged " in a dense packing. Thus US Patent No. 4, 111, 711 discloses the use of sodium tripolyphos phate as dispersing agent for producing a binder containing 25 by weight of aluminous slag of particle size 5 - 50 μ, 38% by

weight of vitrious silica of a particle size from 100 A to 0.1 μ , and 37% by weight of Fontainebleau sand of a particle size of 5 μ, the water/powder ratio being as low as- 0. 175.. The, mortar ..prepared from this mix showed a compressive strength after 20 days of 120 MPa (the testing conditions and specimen dimensions are not stated) .

However.,- -.it- was- -not- known - to. obtairL-corresponding. dense struc¬ tures in systems based on Portland cement, as the usual disper¬ sing agents , - for example sodium tripolyphosphate , are not effective in Portland cement- water- silica systems , such as it has been shown in a series of experiments described in the below Example 7. With the use of extraordinarily large doses of an efficient dispersing agent such as a concrete superplasticiser in accordance with the principles of the present invention, these difficulties have been overcome for Portland cement- silica- water systems , which makes it possible to utilize the above-mentioned principles concerning ex¬ tremely dense or homogeneous packing of ultra fine particles and dense packing of particles being one order of magnitude larger in connection with all products which are nowadays produced from Portland cement-containing matrices such as reinforced concrete, fiber- reinforced concrete and mortar, fiber cement roofings such as asbestos cement roofings , coating panels, grouting mortars etc . , and for production of articles which are nowadays made with more expensive materials such as steel, ceramic materials and plas¬ tics .

Furthermore , it has been found, in accordance with the present invention, that new technological advantages in connection with the shaping of articles and in connection with the reinforcement of ar¬ ticles are obtainable with the utitilization of dense or homogeneous ultra fine particle systems of the type described above, and these discoveries apply not only to Portland cement-based materials , but quite generally to other dense systems , including the above-men¬ tioned known dense systems for which such technological possibi¬ lities have not previously been reported. Hence, novel shaped articles provided through the present invention comprise not only articles containing Portland cement-based binder matrices . When additional bodies C which are not the sand or stone known from

OMPI j. " WIPO

the above-mentioned US Patents No . 4, 111,711 are present in th structures , the invention also comprises such articles even whe containing binders which are not Portland cement-based. In th present context, the term "Portland cement-based" is intended t designate binder systems in which the particles B comprise at leas

20% by weight of Portland cement particles . In addition, the impro vements in the available shaping technologies obviating the use o any excess water, such as it will be discussed in greater deta below, opens up the possibility of more efficient and successf production of certain shaped articles for which it has not previous ly been anticipated to produce them with matrices of homogeneousl arranged or densely packed ultra fine particle systems . In thi connection, novel shaped articles of the present invention als comprise, irrespective of the chemical identity of the particles and B , and irrespective of whether or not additional bodies C ar present, such shaped articles as in situ cast oil well walls; duc fillings, such as in pre-stressed concrete; fissure fillings , such a in mining or engineering; sheets , panels and tiles of thin-walle plane or corrugated shape, especially for use in or on buildings protecting covers applied on steel and concrete members ; pipes tubes ; electrically insulating members ; nuclear shieldings ; and con tainers , all of which novel articles may be produced with grea advantages , both with respect to the production method and wit respect to the properties of the final product, using the technolo gies which have been discovered in connection with the presen invention .

With respect to the incorporation of ultra fine silica dust particle in cement-based binders , already an article from 1952 in "Beto nen" , No . 2, April 1952, volume 17 (issued by Norsk Cementfor ening) , "SiO -støv som cement- tilsaetninger" , disclosed the use o up to 30% of silica dust of a fineness of 0.3 μ in cement. A con siderable increase of the strength of the concrete was noted o incorporation of this powder. However, a very high ratio betwee water and cement plus silica was used, that ' is , from 0.5 to 1 which means that neither the silica dust particles nor the cemen particles were densely packed in the final structures , and th

strength level was 53 MPa after 350 days , which is far lower than in the structures according to the present invention.

German Auslegeschrift No . 2, 730,943 discloses the use of silica dust together with Portland cement of low aluminate content (an

----- - aluminate- conten of less than- - 5% - by • weight)- as cement-bound - matrices and states that, the durability of such materials is in¬ creased due " to the chemical reactivity of the silica. For example, the patent discloses a concrete with about 60 kg of silica dust of 300 kg of cement plus additives with a weight ratio between water and cement of 0.45, which corresponds to a water/(cement + silica) ratio of 0.38, and a 28 days' compressive strength of 85 MPa (as contrasted with a water/(cement + ultra fine particle) ratio of about 0.20 - 0. 14 and a composite strength of at least 130- MPa for concrete and at least 150 MPa for mortar according to the present invention) . The specification of the Auslegeschrift discloses the use of concrete superplasticiser in amounts , the upper limit of which could coincide with the above-mentioned extremely high addition thereof used in accordance with the present invention, . but the Auslegeschrift does not specify any desirability of com¬ bining such high amounts of superplasticiser with the low water/(ce- ent + ultra fine particle) ratios which are necessary to obtain the structures critical to the effects obtained through the present in¬ vention .

The additional bodies C 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 liquid. 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 possibi¬ lity 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 geome-

■ trie identity indicates that the bodies in question ar not subjecte to any substantial crushing or drastic deformation. A typical exam ple is a solid body in the form of a hollow particle or a fibe which in powder compaction or other high stress field treatmen would be crushed or drastically deformed, but which in the muc lower stress field in which the articles of the invention may b formed is capable of avoiding such deterioration.

Examples of additional bodies C which are advantageously incor porated in the articles of the invention are sand, stone, polysty rene 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 ste fibers , plastic fibers , glass fibers, Kevlar fibers, asbestos fibers cellulose fibers, mineral fibers, high temperature fibers and whis kers , including inorganic non etallic whiskers such as graphit whiskers and Al„O„ whiskers and metallic whiskers such as iro whiskers , heavy weight components such as particles of baryte o lead or lead- containing mineral, and hydrogen-rich component such as hollow water- filled particles . When the articles of the in vention comprise additional bodies C , . it may be attractive for op timum strength and rigidity or for other purposes to obtain dens packing of the additional bodies . The easily deformable (easil flowable) matrix rendered possible through the present inventio permits a considerably denser arrangement of additional bodie than was obtainable in the known art.

Especially the incorporation of fibers is of great interest due t the unique capability of the matrix with respect to anchoring fiber

In this context, it should be mentioned that the much dense structure in the articles of the invention will result in a virtu insulation of fibers otherwise subjected to chemical attack from th constituents of the matrix or from the surroundings . The fiber used in the articles of the invention may be of any configuratio such as chopped single fibers , or continous fibers or yarns o ropes , or roving or staple fibers , or fiber nets or webs . Th

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 , however, 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 incorporated. 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 reinforcement in ordinary cement matrices . A far better utilization of the same type of fibers is obtained in the matrix of - the invention, such as described in Example 2. In Example 2, very favourable fixation and resulting strength properties were obtained even though the fiber length was only 6 mm . With the matrix of the invention 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, accordingly, 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 can be characterized as polypropylene fibers having a tensile strength

2 of at least 4000 kp/cm , a modulus of elasticity of at least 7 x ιo 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

fibrillating the stretched material by means of a rotating needle o cutter roller to obtain fiber filaments of from about 2 to about 3 dtex. This technique is disclosed in German Patent Application No. P 28 19 794: 6, and US patent application serial No . 902, 920 of Ma 5 4, 1978. '

Among the most important articles of the invention are the ones i which the particles B comprise at least 50% by weight of Portlan cement particles, especially the ones in which the particles B es

10 sentially consist of Portland cement particles . These very importan kinds of shaped articles (the strength of which is illustrated i the examples) will typically contain silica dust particles in a volum which is about 5 - 50% by volume, in particular 10 " - 30% by volum of the total volume of the particles A and B and will typicall

15 contain sand and stone as additional bodies to form mortar or con¬ crete of extremely high qualities with respect to mechanical strengt frost resistance, etc. , and/or- fibers , especially metal fibers , in- - eluding steel fibers , mineral fibers, glass fibers, asbestos fibers , high temperature fibers , - carbon fibers, and organic fibers, in-

20 eluding plastic fibers, to provide fiber-reinforced products show- ing a unique anchoring of the fibers such as discussed furthe above . With particular reference to fibers which are subject t chemical deterioration, for example glass fibers which are subjec to deterioration under highly alkaline conditions , it is an importan

25 advantage of the present invention that such fibers , both durin the curing of the material and in the final cured material, becom much better protected against influence from the environment, du to partial dissolution of the silica dust with resulting partial neu¬ tralization of the alkaline environment, and due to the micro- dens

30 "jacketing" around the fibers conferred by the ultra fine particles and the coherent structure formed therefrom which very substan¬ tially contributes to static conditions in the glass fiber environmen substantially avoiding any migration of alkaline material against th fiber in the final cured matrix.

35

When the shaped articles of the invention are of large sizes , the are preferably reinforced with reinforcing steel such as bars o

rods or steel wires or fibers . Reinforcements in pre-stressed con¬ structions involving the matrix according to the invention 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

- showin -the - matrix, structur -.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 strongly increased strength of the binder matrix and the strongly improved fixation of fibers and bars in the matrix, possi¬ bilities for producing new classes of reinforced and fiber-rein¬ forced cement based articles and materials are opened up :

l) 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 , Al ? O .whiskers), in- a medium to high volume concentration in o the binder matrix.

2) Semi-brittle materials with high tensile strengths and com¬ paratively 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 inven- tion. In ordinary pre-stressed concrete, the volume of pre- stressing steel is as low as 1 - 2% of the concrete .

The volume of the steel is limited by the compressive strengt of the concrete. An increase of the compressive strength wit a factor of 4 could, for example, be fully utilized in pre stressing members to secure a 4 times higher bending capa 5 city or to decrease the height of the member to one half

Such members would demand a not unrealistic high volume pre-stressing steel (4 - 8%) . It would also be possible t apply the improved matrix material in pre-stressed articles o much smaller cross section than in traditional pre-stresse

10 concretes, with a corresponding use of finer pre-stressin reinforcement (thin wires) . In spite of the larger specifi surface, the wires are well-protected in the new dense matri material which effectively shields the wires from any influenc from the surroundings .

15

4) Articles of reinforced, not pre-stressed concrete where th improved quality of the matrix material is .primarily utilized b

- incorporating steel bars or wires of a much higher tensil strength than in the ordinary steel reinforced concrete. Th

20 nise of an increased amount of an ordinary reinforcement t benefit from the increased quality of the matrix would i many cases demand an unrealistically high amount of reinfor cement. High quality reinforcement bars used in ordinar concrete have a surface which is shaped so as to secure thei

25 anchorage in the concrete (deformed bars ; cam steel; ten to steel; etc. ) . Such bars have a strength not exceeding 90 MPa and, hence, do not have the same high strength as th best cold drawn smooth bars and wires used for example i pre-stressed concrete which typically have strength of 1800

30 2200 MPa. On the other hand, smooth wires and bars do no secure sufficient fixation in ordinary concrete. The strongl improved fixation obtained in the binder matrix according t the present invention opens up the possibility of a benefici utilization of the very high strength smooth steel wires an

35 bars as non-prestressed reinforcement. Due to large strai when fully utilizing the high steel quality and the correspon ding cracks which will occur in the concrete (as in usu

reinforced concrete) it is advisable especially to use the above- mentioned technique in thin members in combination with fine reinforcement in order to secure a crack pattern with several finer distributed thin cracks . 5

- ---. - The reinforcing, -possibility* .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 0 perpendicular to the main reinforcement) in large pre-stressed members .

Due to its extreme tightness and mechanical strength, the material made possible by this invention is useful in a wide range of ar- 5 tides , examples of which are a sheet or panel of thin-walled 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 lining (e. g. , applied as a complete lining) or a refractory lining component (such as a building stone for a refractory lining) ; 0 protecting cover (e . g. to protect other materials against chemical influences) such as a cheap protecting cover applied on steel, e . g. steel tubes or pipes , or on ordinary concrete products so as to supply concrete products with a noble surface which is strong, abrasion resistant, and acts as a sealant against influence from the 5 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 electrically-insulating member; a nuclear shielding for protection 0 against radioactive action (for radioactive-based reactor construc¬ tions , etc. ) ; a seafloor structure for deep water applications ; a container; an in situ cast oil well wall; or a load-bearing member in structural engineering utilizing the extreme strength qualities of the material and its resistance to climatic influence , such as a 5 beam, a shell, or a column, typically as reinforced concrete, espe¬ cially as pre-stressed concrete .

- fR E A OMPI

Seafloor structures for deep water applications , e. g.- spherical con tainers to withstand large hydrostatic pressures require concrete of a high strength, high durability and low permeability .

"Polymers in concrete" , ACI Publication SP-40-1973, P 119-148, re port model tests on small 16 inches diameter spherical hulls mad of high quality polymer-impregnated concrete for deep water appli cations . Full impregnation was obtained by a complicated drying vacuum outgassing-pressure procedure which is , in practice, limi ted to small size members . With the materials and processes accor ding to the present invention, it is now possible to produce suc structures in large scale (several meters in diameter) with a simi lar high quality material by a simple fabrication technique.

While dense packing in the ultra fine particle system has been dis cussed to some extent above, it has also, according to the presen invention , been found that extremely good strength properties ar

* obtainable with densely packed Portland cement, particles and ultr fine particles of silica dust homogeneously arranged in the void between the cement particles , but in a smaller amount than corres ponding to dense packing. -Such a system comprising densel packed Portland cement particles or Portland cement plus addition particles of similar size and homogeneously arranged ultra fine par ticles in the voids between the densely packed particles is believe to be novel per se and has been found to be obtainable by mean of the new technology herein disclosed and involving, inter alia the use of extreme amounts of dispersing agent, vide Example 5 i which excellent mechanical strength properties has been obtaine in systems where the ultra fine particles were present in homoge neous distribution in a densely packed cement matrix, but in a amount smaller than corresponding to dense packing of the ultr fine particles . In the present context, the invention comprise systems in which the amount of homogeneously arranged ultra fin silica dust is as low as down to 0.1% by weight, as even sma amounts of well distributed silica has a beneficial effect whic manifests itself in a high - slope of the strength/silica dust conten

curve at low silica content. The condition for obtain ent of this effect with these very small silica dust amounts is that the system from, which-- . the. ..structure.. js. . made. is. superplasticised, that is , contains a dispersing agent which makes the mass easily flowable

2 in a low stress field of less than 5 kg/cm , preferably less than 2 100 g/cm._ _.- hile-.it- .was. known—to .„ roduce -.certain— dense, materials. with ultra fine particles (silica dust) and powder of cement fine¬ ness , but with less problematic colloidal behavior than a Portland cement, vide the above-mentioned US-Patent No . 4, 111, 711 , it was not known to utilize the improved properties of these materials to obtain various very important technological advances such as , e. g. an improved fixation of fibers , a better shaping of a very dense high porous material (cell concrete) , or for pre-stressed construc¬ tions , etc .

In addition to this , other aspects of the invention comprise me¬ thods which permit either the production of articles which could not be prepared in the known art, and methods which permit the preparation of articles of known structure in an easier way than according to the known methods .

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 parti- des having a diameter of about 5 μ , a structure is obtained which shows an increased resistance against internal mass transport in the form of fluid transport (gas or liquid) between the particles and against mass diffusion in the pore liquid.

In connection with shaping of cement- silica- water suspensions , internal liquid transport in the fresh material is of decisive impor¬ tance. The resistance against viscous flow in systems of particles of geometrical similarity varies inversely as the square of the par¬ ticle diameter.

This means that the time for a given liquid transport under a given pressure gradient in two geometrically similar particle-liquid

systems with a particle size ratio of 1 :50 is 2500 times higher i the fine grained system than in the system with particles whic are 50 times as large .

A similar effect is obtained by filling the pore volume betwee large particles with ultra fine particles, as it is the cross-sectio dimensions of the resulting channels between the particles whic are mainly responsible for the resistance to the flow.

These facts are well-known, and it is also known art to reduce th internal liquid transport in cement/water systems by introducin so-called "thickeners" in the water in the form of ultra fine par ticles or polymers such as Methocell.

Because of the dominating effect of locking surface forces , it will however, normally not be possible to combine the uses of 1) ver dense cement packing and 2) ultra fine particles in an easily flow able aqueous suspension.

However, with an extremely' high dosage of a dispersing agent such as a superplasticiser, this is possible. Thus , easily flowabl cement paste, mortar and concrete with densely packed cemen particles and containing 10 - 30 per cent by volume of silica dust calculated on cement + silica dust, with water /cement + silica- rati 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 quality concrete and morta using relatively high dosages of superplasticiser, an easily flowabl mass having a low water/ cement-ratio (for exampel 0.25) is ob tained. The mass is poured into moulds where it is compacte under the influence of gravity and optionally also mechanical vi bration. However, during this process , the heavier cement, sand and stone particles will tend to arrange themselves in an eve

more dense packing, while water migrates upwardly, the so-called bleeding.

Accordingly, for such known systems with very efficient cement dispersion obtained in the use of relatively high dosages of super¬ plasticiser-, a marked-bleeding- is-normally observed- in spite of th low water/cement-ratio - especially if the process is accompanied by vibration*. This phenomenon may for example be critical in the casting of concrete roads with superplasticised concrete as bleeding results in a surface sludge of high water content, and hence results in a road surface which has a lower quality than the intended abrasion layer. Internal liquid separation is also critical in casting of reinforced concrete with superplasticiser. The liquid 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 silica dust having the above-mentioned particle size, between the densely packed cement particles , and using a high dosage of superplasti¬ ciser, a drastic delay of the bleeding process is obtained, theore¬ tically corresponding to 100 - 1000 times slower water movement. In practice, this means that bleeding has been obviated, consider- ύig that the chemical structuring process normally starts and deve¬ lops much faster.

In other words , utilizing the above-mentioned principle of the invention of combining high dosage of superplasticiser with silica dust, it becomes possible in practice to produce superfluidized high quality con rete, mortar and cement paste without bleeding. This is of special interest in connection with pre-stressed construc¬ tions , where the above-mentioned principles can be utilized for producing high quality non-bleeding, easily 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 quality cement products in a low stress fie and without liquid transport to the surroundings .

In the production of certain cement products , for example asbest 5 cement panels, the known art technique presently used is either slip-casting technique (in which surplus liquid is pressed out fro an aqueous slurry through filters, cf . the Magnani process in wh the pressing- is established via a vacuum system) or a high pre sure extrusion of a moist powder (where a traditional thicken 10 (Methocell) has been added to obviate the otherwise hardly avoi able internal liquid transport at the outlet and the conseque blocking of the system by particle interlocking) .

According to one aspect of the invention, it becomes possible 15 produce such materials in a low stress field by simple rolling pr cesses or extrusion without liquid exchange with the surroundi when a high amount of superplasticiser is incorporated in the ma ■ • together with ultra fine particles .

20 While it might seem possible to employ similar rolling or extrusi processes with cement materials with high amount of superplast ciser incorporated, but without the concomitant use of ultra fi particles which is characteristic to this aspect of the present i vention, such materials - although they could be made easily flo

25 able with a low water /powder-ratio (but not quite as low as wi ultra fine, well dispersed particles) - would, due to the large si of the cement particles , show a marked tendency to local wat expulsion in the stressed zones , such as at the rollers or at t outlet in extrusion, with resulting blocking of the particles . Th

30 has been observed in practice in experiments with a laborato extruder with superplasticised, fine grained cement and with sup plasticised ordinary cement plus an additive of a fine filler whi was finer than the cement, but considerably coarser than the ab ve-mentioned ultra fine silica dust. In both cases , the material h

35 a sandy performance and could not be extruded due to blockin

.

With an ultra fine silica powder incorporated in the superplasticised cement system in accordance with the principles of the present in-

- vention, 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 silica material containing a high

- amount o - superplasticiser- - is -toughly-viseous- and- cohesive- during rolling, while corresponding superplasticised products without the ultra fine silica powder typically 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 cohe¬ rence .

Easily flowable superplasticised cement materials containing ultra fine silica particles are one aspect of the present invention and show a much better internal coherence than corresponding super¬ plasticised easily flowable cement materials without ultra fine silica particles. This is believed to be due to the fact that local liquid transport which contributes to separation, is drastically reduced in the materials with the ultra fine silica particles .

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

The method is known per se and especially developed with super- plasticising additives (without ultra fine powder) . With ultra fine ,

' well-dispersed silica powder in accordance with the principles of - this invention, the process is now much more attractive and shows correspondingly extended potential fields of utility .

The resistance against internal liquid 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 powder materials consisting of well- dispersed Portland cement (s =

4000 cm 2 /g) and silica dust (s = 250,000 cm 2 /g) will show consider-

ably better internal coherence, higher resistance to internal liqui flow and bleeding, and better processability in rolling and extrusi with 20 - 40 volume per cent of silica dust than at 5 - 10 p cent. However, the experience so far obtained indicates that eve very small amounts of ultra fine silica dust (typically 1 - 5%) inco porated between densely packed particles B) , in particular in de sely packed Portland cement structures may have a marked impro ving effect compared to similar materials without silica dust.

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

Grout normally consists of cement and water, usually with admi tures to improve performance. The two main objectives in groutin ducts in post tensioned concrete members are to prevent corrosio of the tendons and to provide bond between the pre-tensione steel and the concrete. The most important properties of the gro to be pumped in the ducts are fluidity and water retention (lo bleeding) .

Fluidity is essentially a function of the water/cement ratio . Re ducing the water content produces a stiff er less fluid mix, t effect being more marked at lower water/cement ratios . In genera the water/cement ratio of good grout lies between 0.35 and 0.50 There are a number of additives such as dispersing agents whic improve the fluidity for a given water/cement ratio, or alternativ ly, reduce the water/cement ratio required to obtain a given flu dity, but their effect on other properties of the grout, especiall the bleeding, often limits their use .

Before grout sets, water can segregate from the mix due to th solid particles being heavier than the water - often terme "bleeding" . This may inter alia result in highly undesirable wate pockets at the underside of the pre-stressed steel. Bleeding increased with increased water/cement ratio and with increase amount of dispersing agent (for example, a fluid cement ^ pas having a water/cement ratio . as low as 0.25 , obtained with a hig

dosage of concrete superplasticiser, shows , in spite of the very low water/cement ratio, marked bleeding) . Anti-bleed-additives are available which- -produce a thixotropic - mix- -exhibiting virtually no bleeding. None of them, however, have hitherto been compatible with a combination of high fluidity and very low water/cement ration-Furthermore.,., most.- of .these_~.additisres-.are..based o .a._cellulo.se . ether which reduces the strength and retards the setting time .

With grout -according to the present invention, (for example a cement- silica-Mighty-grout having a water/cement plus silica dust ratio of 0. 15 - 0.18) , the following is obtained:

1) 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) and protection of the steel against corrosion,

2) the said grout being, in spite of the extremely low water/powder ratio, easily flowable and suitable for being pumped into and fill out the ducts with virtually no bleeding, the additives (ultra fine inorganic particles such as silica dust and a concrete superplasti¬ ciser) having no adverse effect on the setting of the grout, on the contrary ,

3) resulting in a very high early strength.

Finally, the hydration shrinkage for cement paste with water/powder ratio 0.15 - 0.20 is considerably smaller than for pastes with wa¬ ter/cement ratios of 0.35 - 0.50. This means that the expanding additives which are frequently used in grouts to compensate for the shrinkage may not be necessary at all.

Normally, 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 im¬ proved coherence of the fluid mass of the invention with virtually

no bleeding makes it possible to introduce sand into the gro thereby obtaining an even more rigid hardened structure, at th same time retaining an easily flowable grout. This has been de monstrated in an experiment (Example 11) where fluid cohere 5 cement- silica-mortar containing sand up to 4 mm was easily poure into an about 2.5 meter long very narrow duct (18 mm diameter) mainly due to the action of gravity, thereby forming a very dens structure .

10 Along the very same line, the invention makes it possible to pro duce strongly improved prepacked concrete (where voids betwee the pre-placed stones are filled with a fluid mortar) . The improve ment obtained through the non-bleeding highly fluid mortar obtain according to the present invention may be utilized both in dry

15 casting and in sub -water- casting.

The invention also relates to a novel composite material for pro

_D

- - ducing articles of the types discussed above, and shaped article when made from such composite material. In one aspect, the com 20 posite material comprises

A) inorganic particles of a size from about 50 A to about 0.5 μ and

25 B) solid particles having a size of the order of 0.5 - 100 μ , an being at least one order of magnitude larger than the respectiv particles stated under A) ,

a liquid,

30 and a surface- active dispersing agent,

the amount of particles. B substantially corresponding to dens packing thereof in the composite material with homogeneously pack 35 particles A in the voids between particles B , the amount of liqui substantially corresponding to the amount necessary to fill out th voids between particles A and B , and the amount of dispersin

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 ,

and optionally

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

with the proviso that when additional bodies C are not present or are present and consist of sand and/or stone, at least 20% by weight of the particles B are Portland cement particles .

It is to be noted that although the amount of surface active dis- persing agent is defined above 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 super¬ fine particles are obtained from a composite material of the above type -where the particles A are present in a volume substantially corresponding to dense packing to fill the voids between the par- tides B when densely packed.

The surface-active dispersing agent is present in an amount suffi¬ cient to allow 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 substantially corresponds to the amount which will fully occupy the surface of the particles A . Fig. 2 shows ultra fine silica particles covered with a layer of a dispersing agent, a so-called superplasticiser "Mighty" , the composition of which is described below. Under the assumption that the superplasticiser is absorbed in a uniform layer at the surface of the silica spheres , the calculated thickness , with reference to applicant's own experiments , was 25 - 41 Angstrom,

corresponding to a volume of 14 - 23% of the volume of the sphere It is to be noted that a surplus of the dispersing agent over th amount which will fully occupy the surface of the ultra fine parti cles , will not be advantageous and will only tend to take up to much space in the composite material.

Any type of dispersing agent, in particular concrete superplasti ciser, which- in sufficient amount will disperse the system in a lo stress field is useful for the purpose of the invention. The concre superplasticiser type which has been used in the experiments des cribed in the Examples to obtain the extremely valuable results i Portland cement-based systems is of the type comprising alkali an alkaline earth metal salts , in particular a sodium . or calcium salt, o a highly condensed naphthalene sulfphonic acid/formaldehyde con densate, of which typically more than 70% by weight consist o molecules containing 7 or more naphthalene nuclei. A commercia product of his type is called "Mighty" and is manufactured by Ka Soap Company, Ltd. , Tokyo, . Japan. In the Portland cement-base silica dust-containing composite materials according to the inventio this type of concrete superplasticiser is used in the high amoun of 1 - 4% by weight, in particular 2 - 4% by weight, calculated o the ' total weight of the Portland cement and the silica dust.

Composite materials of this type will often contain additional fin particles of suitable size and size distribution together with th

Portland cement particles , such as fine sand, fly ash, and fin chalk, to obtain even more dense binary structures formed fro the particles B in accordance with the principles discussed above

When the additional bodies C are not present, or are present, bu consist of sand and/or stone, the composite material otherwise cor responding to the above-mentioned characterization might coincid with the very special dense composite materials known from U Patent No . 4-, 111, 711 discussed further above and do not constitut part of the present invention . When, however, the composite mate rial .as defined above contains additional bodies which are not san and/or stone, it is believed to be novel, and both with respect -t

its unique shaping and workability properties as discussed above and illustrated in greater detail in the examples below, and with respect, to- its - capability of gently., fixing -and- -thereafter extremely effectively micro-locking or micro- jacketing, in the final shaped state, any incorporated additional bodies, it shows uniquely advan- tageous. 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 pre¬ sent invention .

Especially interesting novel composite materials of the invention are Portland cement-based or not Portland cement-based materials con¬ taining, as additional bodies , bodies selected from the group con¬ sisting of polystyrene bodies , including polystyrene spheres , ex- panded clay, hollow glass bodies , including hollow glass spheres, expanded shale, perlite, natural lightweight aggregate, .gas bubbles , 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 1„0* 3 whiskers and metallic whiskers such as iron whiskers, heavy weight compo¬ nents such as baryte or lead or lead-containing mineral, and hy¬ drogen-rich components such as hollow water-filled 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 will result in important novel mortar and concrete composite materials .

The most important composite materials of the present invention are the materials in which the particles A are silica dust particles

2 having a specific surface area of about 50,000 - 2,000,000 cm /g, in particular about 250, 000 cm 2 /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.

** fEXt OMPI

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 + silica dust, this ratio being 0.12 to 0.30 by weight, -preferably 0.12 to 5 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¬ ticles A + B .-

10 In accordance with a special aspect of the invention, the composite material is packed and shipped as a dry powder, the addition of the liquid, typically water, being done on the job . In this case, the dispersing agent is present in dry state in the composite mate¬ rial. This type of composite material of the invention offers the

15 advantage that it can be accurately weighed out and mixed by the producer, the end user just adding the prescribed amount of liqui and performing the remaining mixing in accordance with the pre-

' ' scrip tion, e. g. , in the manner described in Example 11. This aspect of the invention can be characterized as a composite materia

20 for producing a shaped article (including such special shaped articles as duct fillings, etc. vide above) , said composite material comprising

A) inorganic particles of a size of from about 50 A to about 25 0.5 μ , and

B) solid particles 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) ,

30 and a surface- active dispersing agent,

the amount of particles B substantially corresponding to dense packing thereof in the composite material with homogeneously packe 35 particles A in the voids between particles B , and the amount of dispersing agent being sufficient to impart to the composite materia a fluid to plastic consistency in a low stress field of less than 5

O

WI

kg/ cm 2 , preferably less than 100 g/cm 2 , when an amount of liquid substantially corresponding to the amount necessary to fill out the voids between particles -A and B has been added

and optionally

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

with the proviso that when additional bodies C are not present or are present and consist of sand and/or stone, at least 20% by weight of the particles B are Portland cement particles .

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

A) inorganic solid particles of a size of from about 50 A to about 0.5 μ , and

B) solid particles 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 liquid,

and a surface- active dispersing agent,

the amount of particles B substantially corresponding to dense packing thereof in the composite material with homogeneously packed particles A in the voids between particles B , the amount of liquid substantially corresponding to the amount necessary to fill out 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 , preferably less than 100 g/cm 2 , and mechanically mixing the above

ingredients, optionally together with additional bodies C whic have at least one dimension which is one order of magnitude large than the particles A until a viscous to plastic mass comprising th particles A and B and optionally additional bodies C, has bee obtained,

and thereafter, if desired, combining the resulting mass with ad ditional bodies C which have at least one dimension which is a least one order of magnitude larger than the particles A by me chanical means to obtain the desired distribution of such addition bodies C, and finally casting the resulting mass in the desire shape in a stress field, optionally with incorporation, during cas ting, of additional bodies C which have at least one dimensio which is at least one order of magnitude larger than the parti cles A, - ,

with the proviso that when additional bodies C are not incorporate or are incorporated and consist of sand or stone, the particles comprise at least 20% by weight of Portland cement particles .

Also in connection with this process , the low stress field state above defines the amount of dispersing agent to be used and doe not necessarily mean that the process is in fact carried out in low stress field. ' However, the fact that it can be performed in low stress field constitutes one of the main advantages of the pro cess , and preferred low stress fields (which are preferably belo

5 kg/cm 2 and more preferably below 100 g/cm 2 ) used for shapin the mass are: gravity forces acting on the mass , such as self- le velling out of a cast soft mass, or forces of inertia acting on th mass , such as in centrifugal casting, or contact forces , such a pressure compaction, rolling or extrusion, or the simultaneou acting of two or more of the above forces , such as in combine vibration and pressure compaction. Also, oscillating forces with frequency between 0. 1 and 10 Hz may be used to shape the mass the oscillating forces being of the type described above, such a

• O

4 £

forces from mechanical or hydraulic vibrator, or such oscillating forces may be combined with non-osciHating forces such as in . combined vibration and- pressure compaction.

5 For most practical purposes , the liquid used in the process is

- -water, .and....the».dis.persing. .ag.enL. is ~ of ten .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 incorpor¬ ate the water separately from a solution of the dispersing agent, 0 the dispersing agent being combined with the water in the mixing process . It is characteristic that a mixture conforming with the above-stated definition will 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. 5

The fabrication technique for producing the shaped articles accor¬ ding to the invention mu ' st naturally be specially adapted to the specific type of composite material in question and the specific type of shaped article in question . There are, however, some 0 general trends :

1) The powders of the matrix (particles A and B) should preferably be available as well dispersed as possible before intermixing. If the dispersion in dry condition is insufficient, e. g. if particles A 5 are aggregated, some sort of dispersing action, such as grinding, may be applied.

2) The mixing must secure homogeneous mutual distribution of the solid particles A and B . This may be obtained by dry mixing or 0 by wet mixing where a pre ix of liquid 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 bo¬ dies . In the Examples , which mainly deal with Portland cement-si¬ lica dust systems , the dry mixing technique was chosen . In the 5 examples with concrete and mortar, sand and ' stone were incorpo¬ rated in the dry mix.

3) Incorporation of the liquid either to the dry-mixed powder (par ticles A + B) or to either particles A or particles B in case o pre-mixing of a wet slurry as mentioned under 2) may be perform either by adding the powder to the liquid (preferably under stron mechanical stirring) or by adding liquid to the powder mass (pre ferably under strong mechanical kneading) . Which of these method to be used will largely be a question of experience. However, it i presently believed that in preparing a relatively easily flowin mass from well-dispersed powder, the most easy method is to per form the mixing by adding the well-dispersed powder to the stirre liquid, to avoid the liquid meniscus between particles which woul occur in the reverse ' process in " which small amounts of liquid wer added to the powder. On the other hand, when poorly disperse ultra fine powder is .added to the stirred liquid, the powder ma not be sufficiently dispersed by stresses introduced during stirrin even with addition of dispersing agent. In this case, incorporatio of the liquid in the powder under high shear kneading is preferab as the kneading in combination with dispersing agents may achiev a considerable dispersing- effect. In the Examples (which are mainl based on Portland cement + silica dust) , the method of addin liquid to the powder under kneading/mixing (with a rather modes

2 shear stress of approximately 100 - 1000 g/cm ) was applied. Fo the- most fluid materials (mortar and contrete with water/(cement silica) ratio of 0. 18 to 0.20 by weight) it is believed that the re verse technique might have been used equally well. For the mor stiff mixes (pastes for extrusion containing fibers and with a wate

(cement + silica) ratio of 0.13 to 0.15 by weight) it is , however believed that the reverse technique would not work at all; in thes cases valuable part of the mixing occurred in the extruder where

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

4. The dispersing agent is not necessarily introduced as a solutio in the liquid (it might be added as a powder to be dry mixe together with the particles A and B) . For some systems , it i preferable to wet the surface of the particles with part of th liquid before adding the solution containing the dispersing agent such as it is recommended in the known art with superplasticise

Portland cement suspensions . This was also done in the cement-si¬ lica experiments described in the Examples , except in Example 11. I - is- orthwhile- to note that the mixing- time -of the very dense wet mix may be drastically prolonged compared to traditional mixing. 5 This was in particular the case for the relatively stiff mixes (ex¬ truded -paste— with- -water-/(eement—+ -silica. -dust) - ratio of 0.13 to 0.15, cf. Example 2) and for the medium stiff mixes (water (cement + silica dust) ratio of 0.15 to 0.16, cf . Examples 3 and 9 where a mixing time of approximately 15 and 5 minutes , respectively, was

10 necessary for changing the consistency from an almost dry appear¬ ance to that of a dough and a fluid to viscous mass , respectively . For the concrete with a water/(cement + silica dust) ratio of 0.18, there was also a prolonged mixing time, but not as pronounced as for the very low water/powder ratio systems . It is believed that

15 the local transport of the molecules of the dispersing agent to and between the surfaces of the densely packed solid particles is the time " consuming factor of the prpcess (this transport being more difficult, the smaller the ratio water/powder is) .. The consistency of the material is very -sensitive to the amount of liquid. Thus ,

'20 very small amounts of additional liquid may change the consistency from stiff dough-like to easily flowable. In a superplasticised ce¬ ment-silica mixture, this change can be achieved by changing the water/(cement + silica dust) ratio from 0.14 to 0.18.

25 Introduction of the dispersing agent as a dry powder to the dry mix before adding water seems to be an equally valuable way of producing the casting mass of the invention. This was demonstrated in Example 11 where this procedure was used, resulting in a mortar with substantially the same flowability and appearance as one made

30 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) .

For any specific system, there - is a level at which the system is 35 saturated with superplasticiser and over which there is no benefi¬ cial effect in adding further superplasticiser. This saturation point increases with decreasing water/(cement + silica dust) ratio . Above

this level, the material is not sensitive to the amount of dispersin agent .

5. The incorporation of additional bodies C may be. performed any operational stage such as during the dry mixing or after w mixing etc. The preferred technique to be used in the specif cases depends on the character of the additional bodies C and is question of experience. In the case of concrete and mortar it important to secure a relatively dense packing of the added san and stone in order to secure a relatively small void to be fille with the dense binder matrix of the invention . When incorporatin fine fibers , usual techniques such as shaking/mixing, paddle mixi and kneading mixing may be applied. With incorporation of conti uous fibers or filaments or pre-arranged fibers such as fiber ne or webs , according to ' known technique, a valuable fiber orientati or fiber arrangement is obtainable. Quite generally, the same tech niques may be used for incorporating additional bodies in the ^ mat of the invention as for known matrices, but due to the substanti absence of locking surface forces between the particles, it wi generally be easier »to obtain efficient incorporation.

6. The casting, including compaction " , may be obtained in the lo stress fields mentioned above . The new type of material will b well suited for transportation by pumping due to the substanti absence of bleeding, and the viscous " character of the mass . the casting mass , however, consists of a particulate matter wit virtually no locking surface forces between the individual particle vibration and especially high frequency vibration may strongl assist the casting, as the mutual oscillating displacement of adjace particles will considerably facilitate the flowing.

7. The solidification of the material of the invention differs fro solidification of the corresponding articles based on less densel packed matrices in two respects :

Firstly, as the structure is more densely packed, the solidificatio will be faster (early strength) . Secondly, the solidification may

- CF /.,

influenced by the rather large amount of dispersing agent which is necessary in order to obtain the specific structure. In the Portland cement-silica-Mighty systems , high early strengths was obtained, but a modest retardation of the curing was noted (4 - 8 hours) . I the actual Portland cement-silica-Mighty systems , it was shown, such as- could- -be predicted -fro -th - expected calcium - silicate- hy¬ drate structure to be formed, that extremely good quality could be obtained by "curing at as well approximately 20°C, 80°C and 200°C (autoclave)-, which means that the novel matrix is useful for tradi- tional low temperature curing, heat curing, and autoclave treatment.

Heat curing (which in normal concrete leads to slightly smaller strength than curing at low temperature) seems probably to be the most promising curing technique for the material of the present invention .

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

While the process of the invention can be said to constitute comple- tely new technology, it can also be considered as a valuable modi¬ fication of existing technology . For example in the preparation of fiber cement products according to the Magnani process , shaping (from a dilute cement/fiber/water slurry) through rolling is per¬ formed, with concomitant removal of water by suction . When incor- porating 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 technologies can be modified to produce, by extrusion or rolling at a shaping

2 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 substantially no water is removed from the mass- during the shaping process , and hence, no suction arran-

-ξ fREXt

^ O H_ , WIPO

gement is required.

As indicated above, additional bodies C may be incorporated various stages during the process, and these additional bodies are of the various types discussed in great detail in the precedi text, the only limitation being, or course, that some type of ad tional bodies such as reinforcing bars or tendons in prestress concrete can- only be incorporated during the casting stage and n in any. previous stage.

Unique improved possibilities of submersed, in particular underw construction comprise pouring a cement paste, mortar or concre of the type of the present invention in the form of a cohere mass into a liquid, typically into water in the sea, a harbour a lake, and allowing the mass to displace part of the liquid a arrange itself as a coherent mass .

Other possibilities of utilizing the extraordinary shapeability prop ties of the viscous to plastic mass are to shape articles by sprayi painting, or brushing to shape layers on other articles or to sha an article layer by layer, injection or simple hand application of layer of the mass on a surface and conforming the mass to t shape of the surface. Centrifugal casting technique is anoth attractive shaping method useful in connection with the process the invention.

It is known to increase the strength and improve the properties finally porous materials by impregnation with a liquid which soli fies in the pores of the material.

Thus , it is known to impregnate hardened concrete with polym plastic, and, thereby , to obtain considerably increased streng and durability . The polymerization of hardened concrete is pe formed by pressing or applying, through capillary suction, easily flowable monomer into the porous of the concrete. Usuall monomers of the type methylmethacrylate or styrene are use both of which have very low viscosity. Prior to starting the impr

nation, the concrete must be dried out. When small articles are to be impregnated, they are immersed into a monomer bath, and the infiltration, with.., the, monomer, is. -considerably- improved- by evacuar ting the article prior to the immersion, and an additional improve- ment of the impregnation is obtained by applying pressure to the

■ - . liquid i -.which, the . article, is i_mm.ersed_.- .Subsequent to the.JnfHtrar- tion, the polymerization is performed by heating to about 80°C , for example in a water bath, or by irradiation . When impregnating by means of evacuation and subsequent application of superatmospheric pressure and subsequent polymerization, the compressive strength of usual concrete has been increased from about 30 - 40 to about 130 - 140 MPa. At less complete infiltration, that is , without appli¬ cation of vacuum and subsequent superatmospheric pressure, the improvement of the quality is considerably less .

It is also known to impregnate concrete and similar materials with other liquids . For example, experiments have been performed with application of liquid sulphur. Such impregnations with sulphur have been performed using similar impregnation techniques as mentioned above in connection with dfhpregnation with polymers , and the results , with respect to the increase in strength, have been of about the same order as in the impregnation with plastics .

On the other hand, it is , of course, not known to impregnate the very dense, fine structures of the present invention . From theore¬ tical fracture-mechanical considerations , it can be predicted that an additional filling out of pores with solid plastic or any other solid will give rise to a considerable increase in strength, even though the volume to be filled out is very small. In "Plastimprseg- nerede betonmaterialer II" by Z . Fδrdδs , A . Mikkelsen , K. Singer and A. Winther, March 1970, joint report from Risø and Beton- forskningslaboratoriet Karlstrup , available from Aalborg Portland ' , P . O . Box 165 , 9100 Aalborg, Denmark, is mentioned an increase in the strength of high strength high density diabas concrete prepared by oscillating high pressure compaction from about 100

• MPa to more than 200 MPa by impregnation with polymethylmetha- crylate and other polymers , even though the amount of polymer was as low as 2.2% by weight of the total body impregnated. In ad-

dition, it will, of course, also be possible to improve other proper ties of the novel materials through impregnation, for example abra sive strength and durability. In spite of the extreme density o the novel finely porous materials , impregnation is technically pos sible, such as it is partly theoretically predictable on the basis o the expected structure with internal ducts or pores between th original ultrafine particles A with cross section diameters of 25 100 A, and partly experimentally proved in connection with the lo temperature calorimetric experiments (discussed in Example 2) i which mercury was pressed into dried out sample under pressur in connection with the pores structure investigation, and in whic other exsiccated samples were filled with water under pressure Hence, one aspect of the present invention comprises the impreg nation of the novel very dense structures , using the impregnatio techniques discussed above, and the impregnation articles . thu produced. The said impregnated articles are characterized in tha they contain additional solid substance in the voids of the struct ure formed from the particles A and B . The additional solid sub stance is typically an organic polymer such as polymethylmeth ' acry late or polystyrene, a low-melting metal, or an inorganic metalloi such as sulphur.

In many cases , it is sufficient that the part of the matrix adjacen to exterior surfaces of the article comprises the additional soli substance, and this is also easier to obtain in practice than com plete impregnation throughout the matrix.

The impregnation of the novel structures is performed in the man ner known per se, that is, by partially or completely infiltrating shaped article, comprising a dense matrix of any of the above-dis cussed types , with a liquid and thereafter solidifying the liquid The liquid with which the infiltration is performed is preferably liquid which shows at least one of the following characteristics

It is capable of wetting the internal surface of the structur formed from the particles A and B ,

it contains molecules of a size which is at least one order of magnitude smaller than the particles A,

on solidification by cooling or polymerisation, it leaves a solid 5 substance of substantially the same volume as the liquid,

In accordance with known art measures in the production of impreg¬ nated articles, the efficiency of the infiltration, and thereby, the efficiency of the impregnation, may be enhanced by drying or ap- 10 plying vacuum on the article or the part thereof to be impregnated, prior to the infiltration treatment, or by applying external pressure on the infiltration liquid after contacting the article wit the infil¬ tration liquid.

15 Hence, it will be understood that the present invention covers a wide range of potential fields of utility, from the case where incor¬ poration of a relatively small amount of superfine particles and a - sufficient amount of a dispersing agent results in a dramatic im¬ provement of an existing technology with obtainment of the advan-

20 tages stated above in connection with the explanation of the homo¬ geneous distribution of the ultra fine particles , to the cases where dense packing is obtained between both the ultra fine particles and the particles B , to result in completely novel types of materials having unique properties .

25

When the ultra fine particles are to be densely packed in the struc¬ tures according to the present invention, they are preferably of a size of from 200 A to about 0.5 μ .

30 The ultra fine particles used in the Examples were SiO„ particles formed from vapour phase (in connection with the production of silicium metal in an electric furnace) . Other ultrafine SiOg-containing particles may be used, such as particles prepared by other vapour phase ^ processes such as combustion of silicon tetrachloride with 35 natural gas to form hydrogen chloride and silicon dioxide vapour, or particles prepared as a sol by neutralizing sodium silicate with acid by dialysis , by electrodialysis . or by ion exchange. A list of

- SEA

OMPI / * . WIPO

commercial silica sols is given iri R . K. Her (in "Surface and Collo Science" , editor Egon Matijeviec, 1973, John Wiley & Sons) : "Ludo "Syton" , "Nalcoag", "Nyacol" , "Cab-O-Sil" , "Syloid", "Santocel" "Aerosil" , "Quso" . Various ultra fine particles of other chemic composition are also contemplated, such as finely ground or dis persed natural clay, fly ash from power plants (the finest part o the fly ash) , calcium carbonate, hydrated aluminum oxide, bariu sulphate, titanium dioxide, zinc sulphate, and other fine particles typically particles of the type used in the paint industry. Ther is, however, a preference for particles formed by growth from vapour phase or liquid phase in contrast to particles formed b crushing of larger particles , because particles formed by growt from a vapour phase are likely to have a beneficial shape (spheric in contrast to the irregular shape of crushed particles . Apart fro this , it is normally technically difficult, if not impossible, to grin powder down to the ultra fine size, one μ (micron) often bein considered as a rough lower limit for the grain size which can b obtained by grinding.

The invention is further illustrated in the Examples :

The materials used in the Examples were as follows :

Portland cement: Specific surface (Blaine) about 3300 c (Portland basis 5.78) . Density 3.12 g

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

3 Density (expected) 3.15 g/cm

White Portland cement (ultra fine) : Specific surface (Blaine) 8745 cm /g

3 Density (expected) 3.15 g/cm

E-Cement: A special coarse Portland cement Specific surface (Blaine) about 2400 c

Aluminous cement SECAR 71 : Specific surface (Blaine) 3630 cm /g Density 2.97 g/cm .

Silica dust: Fine spherical SiOg-rich dust.

-Specific -s r£ace (determined by BET

2 technique) about 250,000 cm /g, corresponding to an average particle

3 diameter of 0. 1 ,u. Density 2.22 g/cm . Fly ash from power plants (0007) : Fine spherical particles , part of which are hollow. Specific surface (Blaine)

2 5255 cm /g. Density approximately

2.4 g/cm 2

MICRODAN 5 : Fine chalk (average diameter about 2 μ , density 2.72 g/cm ) .

Quartz sand: Density 2.63 g/cm"

Quartz sand, finely ground: Specific surface (Blaine) 5016 cm /g

3 Density 2.65 g/cm

Might : A so-called concrete superplasticiser, sodium salt of a highly condensed naphthalene sulphonic acid/formaldehyde condensate, of which typically more than 70% consist of molecules containing

7 or more naphthalene nuclei. Density

3 about 1.6 g/cm . Available either as a solid powder or as an aqueous solution

(42% by weight of Mighty, 58% by weight of water) .

Steel fibers : Wirex-Stahlfaser, diameter 0.4 mm,

3 length 25 mm . Density about 7.8 g/cm .

Water : Common tap water.

Polypropylene fibers : Fibers prepared as described in Example 4.

Example 1 ,

Preparation of cylindrical concrete specimens from wet concre mixed with silica dust/cement.

Concrete specimens were prepared from four 35 liter batches , eac of the following composition .

per batch per m

(gram) (kg) (liter)

Silica dust 4.655 133 60.5

Portland cement 14.000 400 128.2

Quartz sand - 4.935 141 53.4 (1/4- 1mm)

Quartz sand 19.810 566 214.4 (1-4 mm)

Crossed granite 40.355 1153 427.0 (8-16 mm)

"Mighty" (powder) 72.5 13.5 8.4

Water 3500 100 100

From each batch, 16 cylindrical concrete specimens (diameter 1 cm, height 20 cm) were cast.

Comments on the above composition : —

To obtain a dense packing of the binder, about 32 per cent b volume of the fine powder (silica dust) and about 68 per cent b volume of the coarse powder (Portland cement) was used. In ord to avoid dilution of the binder, relatively coarse sand without fin under 1/4 mm was used. In the coarse materials gap grading w

utilized (the composition does not contain any material between 4 and 8 mm) , and the sand/course aggregate ratio was adapted in order" to ' obtain- a dense structure with " minimum- binder volume . In consideration of the dense packing, the amount of binder (Portland

3 cement plus silica dust) was reasonably low (533 kg/m ) . The

dosage" of^Mighty"- permitted- the -σb-tainment- of- a~ very "soft; easily cast concrete with low water content (water /powder ratio 0.19 per weight) . (Later experiments have indicated that the amount of water may be kept considerably lower for concrete to be cast with traditional vibration technique, for example 80 liter/m 3 instead of the 100 liter/m used in this Example) .

The procedure was as follows :

Mixing: Coarse aggregate, sand, cement and silica dust were dry- mixed in a 50 liter paddle mixer for 5 minutes . Thereafter, part of the water (about 2000 grams of the total 3500 grams) was admixed, and mixing was continued for 5 minutes . Concomitantly with this , a solution of 472.5 grams of "Mighty" powder in 1000 grams of water was prepared by shaking for 5 minutes on a shaker mixer. The

"Mighty" solution and the remaining about 500 grams of water were added to the mixture (the last water was used for washing the container containing the "Mighty" solution to ensure that the entire amount of "Mighty" was utilized) .

Fresh concrete: The concrete was soft and easily workable. The consistency of the concrete was determined by measuring the sprea¬ ding cone (DIN 1048 Ausbreit-Mass , 20 cm cone, diameter 13 cm - 20 cm) . The spreading measure was 27 cm - 30 cm . On the first batch, the content of air was measured (1.5%) .

Casting: 16 concrete cylinders having the dimension stated above were cast from each batch. The specimens were vibrated for 10 - 20 seconds on a vibrating table (50 Hz) .

Curing: Immediately subsequent to casting, the closed molds were submersed in water. Some of the specimens were cured in water at

80°C , while other specimens were cured in a partially water-fille autoclave at 214°C and a pressure of 20 atmospheres , and anothe portion of the specimens were cured in the normal way in water a 20°C .

Various curing times were used. The specimens cured in water a 20°C were demolded after about 24 hours , and their density wa determined by weighing in air and submersed in water, whereafte the specimens were again placed in the water for further curing

The heat-cured specimens were removed from the water bath afte 20 hours and cooled for about 1 hour in water at 20°C, whereafte they were demolded, and their density was determined by weighin in air and submersed in water, respectively. Part of the specimen were thereafter subjected to strength testing etc.

A single specimen was autoclaved for about 96 hours under th conditions stated above, whereafter it was cooled and demolded an weighed in air and submersed in water for determination of densit whereafter it was subjected to mechanical testing.

Testing.

Density , sound velocity, dynamic modulus of elasticity, compressiv strength and stress/strain curve were determined. The compressiv strength was determined on a 500 tons hydraulic press .

In the table below, the strength values for the various curin times are stated.

TABLE I

Compressive strength measured on 10 0 x 20 cm water-cured conc cylinders , cured and tested at 20°C .

O

Curing time Compressive Number of Standard days strength (MPa-) specimens deviation (MPa)

1 26.9 10 1.72

14 115.9 6 3.71

28 124.6 10 4.16

84 140.4 4 2.23

169 146.2 2 6.19

10 specimens water-cured at 80°C for 20 hours were subjected to determination of compressive strength . The average compressive strength determined was 128 MPa.

One specimen autoclaved for about 96 hours at 214°C/20 atmospheres was found to have a compressive strength of 140 MPa.

The density of all samples was closely around 2500 kg/m . Calcula- tions showed that this density corresponds to a dense packing with low air content (probably below 1-2%) .

For specimens water-cured at 20°C , the sound velocity was about 5.2 km/sec , and the dynamic modulus of elasticity was about 68, 000 MPa.

Comments on the test results .

The experiments and the test results show that the water require- ment of the concrete with the new binder combination is very low

(water/powder ratio 0. 19 by weight) , even though the concrete was easily flowable (had a high slump) .

The mechanical properties of the cured material, especially the strength, was far better than for conventional "super concrete" cast with 600 kg of cement and superplasticising additives .

To the applicants' best knowledge, the highest compressive streng of concrete fabricated with traditional casting and curing techniqu recorded until now is 120.6 MPa measured on test cylinders of th same dimensions as above and consisting of concrete with a water

3 cement ratio of 0.25, a cement content of 512 kg/m , and a conten of "Mighty" 150 in an amount of 2.75% of a 0.42% solution, calculat on the weight amount of cement, the samples having been store for one year prior to the testing of compressive strength. (Kenich

Hattori, "Superplasticizers in Concrete, Vol. I, Proceedings of a international Symposium held in Ottawa, Canada, 29-31 May, 1978 edited by V.M. Malhhotra, E .E . Berry and T . A . Wheat, sponsore by Canada Centre for Mineral and Energy Technology, Departmen of Energy, Mines and Resources , Ottawa, Canada and America

Concrete Institute, Detroit, U . S .A . ) .

Example 2.

Preparation of fiber-reinforced silica dust/cement specimens .

Fiber-reinforced specimens were prepared with the following com¬ position :

Experiment No . 1 2 3

(% by weight, dry basis)

6 mm polypropylene fibers 2.2 3.0 3.0 (140 g)

Silica dust 23.8 23.6 24.5 (1715 g)

E- Cement 71.6 70.9 75.5 (5145 g)

Mighty 2.4 2.4 2.7 (186 g)

Water/ dry matter-ratio 0.157 0.157 0. 13 (water 910

Experiments 1 and 2 were made using batches of about the sam size as stated for Experiment 3.

O

In a kneading machine with planetary movement, the cement plus the silica dust were dry mixed for 5 minutes with a mixing blade .

Thereafter, the major portion of the water which did not form part of the Mighty solution was added, and mixing was continued for 5 minutes -with a- ixing hook.

The Mighty 'solution and the remainder of the water (about 50 ml) were added, and mixing was continued with the mixing hook until a dough-like consistency had been obtained (8 - 15 minutes) .

The fibers were added to the dough while mixing with the mixing hook, and thereafter, the mixing was continued for 5 minutes .

The resulting mass was extruded into strings with a cross-section of about 4 x 1 cm in a laboratory extruder at a pressure not ex-

2 ceeding 2 kg/cm .

Immediately subsequent to the .extrusion, the material was covered with plastic film . About 1 hour later, the extruded strings , which had a length of 1 - 2 meters ' , were cut in lengths of about 20 cm and stored in a moist box at 20°C for about 24 hours . Thereafter, they were subjected to various types of storing:

i) Storing in water at 20°C/or in 100% relative humidity at 20°C .

2) Storing at 100% relative humidity at 20°C .

3) Steam curing at 80° C at 100% relative humidity for about 24 hours .

4) Autoclaving at 130°C for about 48 hours for Experiments 1 and 2 and at 125°C for 60 hours for Experiment 3.

Testing.

Most of the samples were tested in bending tests in which th curvature of the specimens was determined as a function of th load. A 4-point load with a support distance of 19 cm and a loa distance of 10 cm was used. The testing machine was a deformatio controlled machine, ZWICK 1474.

One specimen from Experiment 1 and one from Experiment 2 wer tested in pure tension in the above machine. Force/deformatio diagrams, were recorded.

Rupture surfaces were subjected to scanning electron microscopy

Test results .

In the below table, sigma M designates the formal maximum tensil stress in bending at which the matrix cracks (break in the stress strain curve) . Sigma^ designates the formal maximum tensile stres at maximum load. E M is the modulus of elasticity before crack o the matrix. Sigma designates the tensile strength .

TABLE II

Experiment

Temperature, °C 20 80 130 20 80 130 20 125

Relative humidity, % 100 100 aut. 100 100 aut. water aut.

Days 1 48 h . 48 h. 60 h

Sigma M MPa 9.8 12.0 22.7 10.2 14.0 18.7 13.6 26.4 Sigma- MPa 18. 1 19.0 27.6 16.2 19.0 24.1 21.4 26.4

J M GPa 10.5 23.9 10.6 19.2 19.6 34.0

*) autoclaving

Fig. 3 shows a diagram of bending stress versus deflection of one of the specimens from Experiment 3 cured at 20°C for 7 days . Thickness 10.6 mm . As ordinate is shown the formal bending stress and as abscissa deflection. Until fracture of the matrix, the plate was very stiff . Hereafter, the load was largely carried by the fibers; -and the specimen was able- o— carry an 'excess load of 57% " while it was deflected 1 mm measured over a length of about 60 mm.

Fig. 4 is a stress/strain diagram for the specimen made according to Experiment 1, cured at 80°C for 1 day, and the specimen made according to Experiment 2, cured at 80°C for 1 day, respectively, in tension . The material was very stiff until cracks occurred in the matrix. Hereafter, the load was carried by the fi * bers .

Fig. 5 is a scanning electron microscopy photograph of a 30 , u thick polypropylene fiber at rupture surface of one of the speci¬ mens .

One specimen from Experiment 3 cured at 20° C for 7 days was further cured under substantially the same conditions for about 3 weeks and was thereafter subjected to a determination of the amount of freezable water.

The testing was performed by differential calorimetry, the specimen being cooled down to -50°C . Only very little freezable water was determined, viz. 5 g per gram of specimen freezing at between -40 and -45°C . A material showing such properties must be desig¬ nated as absolutely resistent to frost attack.

Example 3.

Experiments were made with various types of fine filler in order to determine the water demand necessary to obtain the fluid to plastic consistency of the mass to be cured . The following four series were performed:

υ &E , OMPI

^v irw ER lx

1) Casting of cement mortar with silica dust.

2) Casting of cement mortar with the same volume (as the silic dust in 1)) of relatively fine chalk "Microdan 5" which is somewha finer than the cement, but not nearly as fine as the silica dust

3) Casting of cement mortar plus filler (same volume concentratio as the fillers in 1) and 2)) of the same fineness of cement (as th filler is Portland cement proper (reference mixture)) .

4) Casting of a similar mixture . s in 1) , but of a somewhat softe consistency, and including chopped steel fibers in a volume conce tration from 1 - 5%.

In all of the series , the following common components were use

(with reference to one batch; for series 4) , batches of double siz were used) :

Quartz sand: 1 - 4 mm 2763 g

0.25 - 1 mm 1380 g

0 ' - 0.25 mm 693 g

Portland cement: - 2706 g

Mighty (dry powder) - 107 g

The following components were different:

Series 1 Filler: silica dust 645 g water * J ) (total) 444 g

Series 2 Filler: Microdan 5 790 g

-x. water (total) 620 g

Series 3 Filler: Portland cement 906 g water ' (total) 720 g

Series 4 Filler: silica dust- 645 g

(softer mortar water *) J (total) 570 g for fiber re- steel fibers 250-500-1000-1242 g inforced tiles)

*) The amount of water was determined with respect to obtainment of the same consistency in mixing and casting.

Mixing and Casting.

- The. mixing -was. performed- in - a~ kneading machine, .with planetary movement, using a mixing blade. The following procedure was followed :

1) Dry mixing of sand, cement + filler for 5 minutes .

2) Addition of the major portion of the water which does not form part of the Mighty solution . About 50 ml of the water is kept for later use as rinsing water. Continued mixing for 5 minutes .

3) Addition of Mighty solution (mixed on shaking mixer 107 g of Mighty + 215 g of water - or multipla hereof) with subsequent rin¬ sing of the container with the above-mentioned 50 ml of water to secure that all of the Mighty is incorporated in the mixture . Mixing for about 10 minutes .

The mortar mixtures in Series 1 , 2, and 3 behaved like a highly viscous fluid and were cast in cylindrical moulds on a standard vibrating table (50 Hz) . The casting time was about 1 minute. The specimens (in closed moulds) were cured in water at 20°C . The mortar mixtures in Series 4 (double size) were considerably softer.

In Series 4, steel fibers were poured into the mixing vessel after curing the final mixing of the mortar. Four different dosages were used, that is , 1 , 2, 4, and about 5% by volume, respectively .

Mixing was continued for additionally 5 minutes , whereafter tiles of 5 x 30 x 40 cm were cast on vibrating table .

After curing for about 24 hours in the moulds (cylindrical and tile moulds) , the specimens were taken out and their density was deter¬ mined by weighing in air and submersed in water, respectively .

-« tr _OMPI__

The following table gives an impression of the packing density i the various mortars :

TABLE III

Series No . Filler type silica Microdan Portland silica dust 5 cement dust

Consistency plastic plastic plastic soft to viscous to viscous to viscous

(volume ratios) -

Fluid*) 0.44 0.74 0.84 0.55 Solid J

Fluid*) 0.31 0.42 0.46 0.35

Solid + fluid

Solid ' 0.69 0.58 0.54 0.65

Solid + fluid

Water x pw

0.12 0.17 0.20 0. 16 Solid x pc

*) Mighty is included as fluid, referring to dissolved state.

**) Solid is cement + filler.

pw:- The density of water.

pc: The density of cement.

The volume ratio ,. , varies from 0.44 with the extremely fin silica dust via 0.74 for the material with a filler which is only little finer than cement, to 0.84 for the reference mortar in whic the filler is cement. This is in complete conformity with experienc

from packing of large particle systems . The same is expressed in another form in the two last rows . It is interesting to note that the so-called- water/cement ratio (weight ratio between water and cement) would be as low as 0. 12 for the silica cement system if silica had the same density as cement, versus 0.20 for a pure

- cement, in -spite of the- fact -that this- volume (0.20) is extremely low and only obtainable with a high dosage of superplasticiser.

The density measurements indicate that the mortars in the above experiments were densely packed without any significant amount of entrapped air (s 1.2%) . The following densities were found:

Series 1 silica dust -3

2446 kg/m ι Series 2 Microdan 5 2424 kg/m" Series 3 cement 2428 kg/mj; Series 4 silica dust + 1% steel fibers 2449 /m^ 2% " " 2484 kg/m 5 4% " 2619 kg/m" about 5% " " 2665 kg/m'

The amount of Mighty in the above materials is high such as ap¬ pears from the below ratios :

Mighty Filler 0.23

Mighty 0.06

Total solid

Mighty Water 0. 15

This shows that the dispersing agent (organic molecules) takes up much space, that is , 15% relatively to the water, and more than 20% relatively to the fine filler.

To obtain an indication of the quality of the cement/silica dust mortar, one of the cylinders from Series 1 was tested in compres¬ sion after curing in water at 20°C for two days and autoclaving at 214°C and 20 atm. for about 24 hours (in water) . The compressive strength was found to be 161.2 MPa.

Example 4.

Preparation of the polypropylene fibers used in Example 2.

The polypropylene used was GWE 23 from ICI with melt index of 3 g/10 minutes measured according to DIN MFI' 230/2.16.

In a standard extrusion/stretch plant, the polypropylene was ex¬ truded into a blown tubular film at an extruder temperature of 180 - 220°C, and the tubular film was cooled with cooling air at 18 - 20°C and cut into two film bands .

From the drawing station following the extruder the film was passe through a hot air oven with ' an air temperature of 180°C and an air velocity of 25 m/second. By' using a higher roller speed in the stretch station following the hot air oven, the film was stretched in a ratio of 1 : 17. Thereafter, the film was heat- stabilized by passing a hot air oven with an air temperature of 180° C and an air velocity of 25 m/sec . , the film velocity being about 90 /sec . The thickness of the film was then 20 -u.

The film was fibrillated to form fibers of from 2 to 30 dtex by means of a Reifenhauser FI-S-0800-03-01 fibrillator with 13 needles per cm in each of two consecutive staggered needle rows placed with the same distance as the interval between two needles . The fibrillation ratio (= the ratio between the film advancing velocity and the circumferential velocity of hydrophilic avivage (Henkel- LW 421)) was applied as an 1 : 9 aqueous slurry, and the fibers were cut in lengths of 6 mm in a staple cutter.

Example 5.

Experiments -were performed with varying silica/silica + cement-ratio using concrete of the same composition as in Example 1 with respect to stone, sand, total volume amount of powder (Portland cement + silicaX.and- Mighty.. . .

In- the experiments , the ratio silica to Portland cement + silica was varied between 0, 10, 20, 30, 40, and 50 per cent by volume . In the individual cases , the amount of water ' was adapted so that the fresh concrete obtained had substantially the same consistency (as measured by spreading cone) as in Example 1. The mixing and casting procedures were as in Example 1.

From each of the 6 compositions , two 35 liter batches were made and cast in 16 concrete cylinders of 10 x 20 cm which were tored in water at 20°C .

For each mixture, two samples were tested after 28 days , which means that for each of the 6 compositions 4 specimens were tested.

The deviation of the experimental results was of the same order as in Example 1.

The mean values appear from the below table :

TABLE IV

Compressive strength of 10 x 20 cm concrete cylinders containing varying amounts of silica dust in concrete with constant total volume of Portland cement + silica. Test specimens stored in water at 20° ' C for 28 days .

'

OMPI

Volume ratio between silica and silica + cement, per cent 0 10 20 30 ' 40 50

Compressive strength, MPa 84. , 5 109. .6 118. .5 119. .0 117.2 112.9

Example 6.

Small specimens of a complex shape (an 1 :40 model of a. tetrapode to be used in hydraulic model experiments in connection with har- bour construction) were cast from an ordinary superplasticised cement mortar with low water/cement- ratio . An extremely high amount of superplasticiser was used. When the casting was finished it was observed that internal liquid transport had taken place with resulting bleeding .and ' internal separation, resulting in models having a poor quality surface.

The same procedure was repeated, but this time replacing 10 per cent of the cement with silica dust, while still using an extremely high amount of superplasticiser. This time, no bleeding occurred, and a completely satisfactory surface was obtained.

Example 7.

Comparison of mortars made with Portland cement and aluminous cement .

Experiments were made with two different dispersing agents - Mighty and sodium tripolyphosphate - used in silica-cement mortars with Portland cement and aluminous cement, respectively, to ascer¬ tain the water demand necessary to obtain fluid to plastic consis¬ tency of the mass to be cast.

O .. WI

The following 5 series of experiments were performed:

1. Casting of cement mortars with a-binder matrix consisting of 2706 g of Portland cement and 645 g of silica dust in five- different batches containing 164, 82, 41 , 20.5 and 0 g, respectively, of Mighty - (dry powder) . - -

2. Casting' of cement mortars with a binder matrix consisting of 1813 g of Portland cement and 1290 g of silica dust in five diffe- rent batches containing 164, 82, 41, 20.5 and 0 g, respectively, of

Mighty (dry powder) .

3. Casting of cement mortars with a binder matrix similar to series 2, with the exception that the Portland cement" was replaced with 1725 g of aluminous cement and that the batch containing 20.5 of

Mighty was omitted.

4. Casting of two batches of cement mortar with a binder matrix consisting of 1290 g of silica dust, the two batches containing almost the same amount of sodium tripolyphosphate (14.4 and 12.8 g, calculated on dry powder) ' , but with different types of cement, that is , 1725 g of aluminous cement in the first batch and 1813 g of Portland cement in the second batch.

5. Casting of four batches of mortar with a binder matrix containing

3626 g of Portland cement without silica dust, using 82, 41, 20.5 and 0 g, respectively, of Mighty (dry powder) .

In all of the 5 series , the following common components were in- eluded (with reference to one batch) :

Quartz sand 1 - 4 mm 2763 g

0.25 - - 1 mm 1380 g

0 - 0.25 mm 693 g .

The volume of fine powder (cement + silica dust) was the same in

3 all mixes , namely approximately 1160 cm .

The water demands , that is , the amount of water used in the var ious mixes in order to obtain the specified consistency, were ascer tained by trial mixing. The water demands appear from the table The right hand column states the volume of water in relation t the volume of cement + silica dust.

Mixing.

The mixing was performed in a kneading machine with planetar movement using a mixing blade. The following procedure was fol lowed for ' batches with Mighty:

1) Dry mixing of sand, cement + silica dust for 5 minutes

- 2) Addition of the major portion of the water and continue mixing for 5 minutes (as in Example 3) .

3) Addition of a solution of the dispersing agent (a solutio of Mighty powder in water in the weight ratio 1: 2) an mixing for 10 - 20 minutes .

For batches containing no dispersing agent, wet mixing for 5 - 1 minutes was performed. For batches with sodium tripolyphosphate 400 - 450 g of a 3.2% solution of sodium tripolyphosphate wer added directly to the dry mix. For the mixes requiring more water this was added afterwards during the wet mixing.

The consistency was evaluated by measuring the spreading of cone of the material formed by pouring the material into a 5 c high brass cone mould with bottom diameter 10 cm and upper dia meter 7.1 cm on a flow table with brass surface for use in testin hydraulic cement (ASTM C 230-368) and removing the mould. Th diameter of the material was measured a) immediately subsequent t removal of the mould, and b) after 10 strokes and c) after 2 strokes .

The consistency was considered to be of the desired value for dia¬ meters of about 14 cm after 10 strokes and of 16 cm after 20 stro¬ kes .

In some of the cases , the water demand was determined by inter¬ polation- f om- -tests with too- -much- -water-- (toσ -large - a- diameter) and too little water (too small a diameter) .

TABLE V

Water demand expressed in grams of water per batch and in rela¬ tion to the total amount of fine powder (cement + silica dust) on a volume basis , the volume of fine powder being the same in all of

3 the mixes (1160 cm )

Series No . 1 2706 g Portland cement 645 g silica dust

Mighty (powder) Water demand' grams gram volume ratio

164 500 0.43

82 500 0.43

41 530 0.46

20.5 710 0.61

0 1200 1.03

Series No . 2 1813 S Portland cement

1290 S silica dust

OMPI

Mighty (powder) Water demand grams &r s volume ratio

164 550 0.47 82 . 550 0.47 41 580 0.5Q

20.5 860 0. ~ 74 .0 1500 1.29

Series No . 3 1725 g aluminous cement 1290 g -silica dust

Mighty (powder) Water demand grams grams volume ratio

164 490 0.42

82 490 0.42

41 >530 >0.46

0 1090 0.94

Series No . 4 1290 g silica L dust approx. 14 g sodium tripolyphosp

(STP)

Cement + STP (powder) Water demand grams grams , volume ratio

λ r

aluminous cement 1725 >436 >0.37

+ STP 14.4

Portland cement. 1813

+ STP 12.8 >1287 ** <1.11

*) When visually evaluated, the mortar appeared sufficiently fluid, but the diameter of the cone was only 10 cm.

**) The mixture had consistency as stiff foam. Upon further addition of 40 g of the Mighty solution 1 : 2, this mix became easily flowable .

Series No . 5 3626 gram Portland cement no silica dust

Mighty (powder) Water demand grams grams volume ratio

82 760 0.66 41 760 . 0.66 20.5 840 0.72 0 « -> 1140 0.98

Comments on the test results .

1. Mixes with Portland cement, silica dust , and relatively high amounts of Mighty have a very small water demand: 0.42 - 0.47 on a volume basis (corresponding to a water/powder ratio of 0. 15 - 0.18 on a weight basis) .

-g pREA c

OMPI

2. In comparison with mixes without dispersing agent, the wate demand is reduced to between half and 1/3.

3. Compared with mixes without silica dust (only Portland cement) the water demand for mixes with 30 and 50% by volume of silic dust, respectively, without Mighty is 5 and 32 per cent higher respectively, than for mixes with a neat cement, while the wate demands for the corresponding mixes with a high dosage o Mighty are 34 and 28 per cent smaller, respectively, than fo the corresponding mixes with neat cement and high dosage o

Mighty.

4. In a system of aluminous cement and silica dust, the same lo water demand is obtained at a high dosage of Mighty as in system of Portland cement and silica dust.

5. Sodium tripolyphosphate has a beneficial influence on mixes o aluminous cement and silica dust, but is without any effec (high water demand)- on corresponding mixes with Portlan • cement.

Example 8.

Freezing tests on concrete cylinders .

A concrete cylinder having a diameter of 10 cm and a height of 2 cm was made with Portland cement, silica dust and Mighty (a spe cimen from the same charge as described in Example 1) . Befor testing, the cylinder was stored in water at 20°C for almost months . Together with 4 reference specimens , the cylinder wa subjected to a very tough freezing test which normally destroys al concrete in less than 2 - 3 weeks . The reference specimens were cylinder of diameter 15 cm and height 30 cm of a concrete with " water/cement ratio of 0.7, 1 cylinder of diameter 15 cm and heigh 30 cm of a concrete with a water/cement ratio of 0.4 and 2 cylinde

f»,

of diameter 10 cm and height 20 cm of a high quality concrete with

3 600 kg cement/m and a water/cement ratio of about 0.25 produced

-with a- high- dosage -of Mighty, but without- -silica. All of these spe¬ cimens had been cast previous to the sample with cement, silica dust and Mighty .

The testing involved the following exposures :

Each Tuesday, Wednesday and. Thursday, the following cycle was performed: thawing in a 7.5% NaCl solution at 20°C from 8 - 10 a.m .

drying in a an oven at 105 °C from 10 a.m. to 2 p .m .

storage in a 7 5% NaCl solution at 20°C from 2 to 4 p .m.

storage in a freezer at -20°C from 4 p .m. to 8 a.m . the next day

Each Friday, the following cycle was performed: thawing in 7.5% NaCl solution at 20°C from 8 to 10 a.m .

drying in an oven at 105 °C from 10 a.m . to 2 p .m .

storage in 7.5% NaCl solution at 20°C until Monday at 10 a.m .

The destruction of the specimens was assessed- visually and by measuring the ultrasonic velocity (decrease of ' the ultrasonic velo¬ city indicates destruction of the structure) .

Results .

After 3 weeks : all of the rerefence specimens had been destroye the destruction stage being defined as the stage at which t ultrasonic velocity has decreased to less than half of the origin value . The ultrasonic velocity in the silica dust- containing specim was substantially unchanged.

After 3 months , the ultrasonic velocity in this specimen was st substantially unchanged.

After 6 months , the ultrasonic velocity had decreased to abo 65%, and only after about 9 months, the ultrasonic velocity h decreased to half of the original value .

Comments on the test results .

The experiments indicate that concrete and similar products prod ced with the new dense -cement- silica matrix has a strongly impr ved resistance to freeze- thawing compared to corresponding pr ducts produced with traditional cement binder matrix.

Example 9.

High quality mortar.

Four different mortar mixes were prepared, all on the basis white Portland cement, silica dust and Mighty, but with differe types of powder as replacement for some of the white Portla cement:

In all of the mixes , the following common components were us (with reference to one batch) :

Mr

Quartz sand 1 - 4 mm 2763 g

0.25 T 1 mm 1380 g

0 - 0.25 mm 693 g

Silica dust . .. 645 g

42% Mighty solution 195 g

Water 387 g

The following components were different:

Mix No . 1

White Portland cement 2706 1804 1804 1804

Fine fly ash (5255 cm 2 /g) 694

Fine sand (5016 cm 2 /g) 765

Fine white cement (8745 cm 2 /g) 902

The volume of the " fine powder was kept constant at about 1160 cm .

Mixing.

The mixing was performed as described in Example 7. The consis¬ tency was soft.

Casting and curing.

From each batch, 2 cylinders of diameter 10 cm and height 20 cm were cast with slight vibration . The cylinders from mix No . 1 were stored in a closed mould for approx . 4 days at 60°C and 2 days in water at 20°C , while the remaining cylinders ' were stored for 22 hours at 80°C in the closed mould.

OMPI /,, WIPO

Testing.

The compressive strength was determined. The results appear fro the table :

Mix - 1/3 of the cement Compressive No . replaced by Curing strength (MPa

1 - 4 days 60° C 179

2 fly ash 22 h. 80°C 160

3 fine sand 22 h. 80°C 150

4 fine cement 22 h. 80°C 164

Comments on the test results .

The experiments demonstrate a very high strength of the binde matrix. In all cases , the fracture went through the quartz particle which means that the strength level can undoubtedly be considerab increased by using a ' stronger sand material. In addition, th results demonstrate the possibility of replacing part of the Portlan cement with a different powder of a fineness like that of cement o somewhat finer (fly ash and finely ground sand) . Finally, th results demonstrate the possibility of utilizing an altered cemen grain size distribution, in this case demonstrated by replacing 1/ of the ordinary white Portland cement with a finely ground whit Portland cement.

Example 10.

Fixation of smooth 6 mm steel bars .

Very smooth 6 mm diameter steel bars were cast into silica- cemen mortar (compressive strength 179 MPa) prepared as described i

Example 9, Series 1, nd into reference mortar (compressive stren 38 MPa) , prepared from ordinary mortar with the same type o

white Portland cement, but without silica dust and without Mighty , and having a water/cement ratio of 0.5. The bars were cast into the mortar to a- depth of- 60 mm, 100 mm of the bars protruding from the specimen for fixation in a testing machine. The silica cement mortar and the reference mortar samples were stored as stated- in- .Example..9., Series 1-.- prior to testing.

In an Instron machine, the force necessary for drawing the steel bars out. of the mortar, and the force/ displacement curves were recorded. From these data, the work involved in the drawing out operation, the average shear stress along the surface of the steel bars , and the tensile stress in the steel bars were calculated.

The results appear from the below table, the work stated being the work necessary for 10 mm drawing out of the steel bars :

Max. force Work Max . ave¬ Max. average

Type of mortar KN NM rage shear tensile stress stress in bars

MPa MPa

Cement- silica 9.25 61.5 8.19 327

Cement- silica 9.25 56. 1 8.19 327

*

Cement- silica 5.00 42.0 4.42 176

Reference 1.66 5.8 1.47 52

Reference 2.13 8.2 1.88 75

* The results of this apparently uncharacteristic experiment are not included in the below comments on the results .

Comments on the results .

The experiments were performed with steel bars which are consi¬ derably smoother than the reinforcement used in ordinary rein-

- QREAlr OMPI_

forced concrete (with a surface appearing like polished steel an without any corrosions) . In spite of this, an extremely good fixati of the bars in the silica-cement mortar was obtained. In spite o the very short depth to which the bar was cast in the specimen (6 cm) , a force corresponding to about 70% of the yield stress o the steel was required to draw out the bars . It will be noted tha the resistance to drawing out is 4 - 6 times higher that in th reference mortar, which is about the ratio between the compressiv strength of the materials . The work necessary for drawing out th bars was additionally increased, as this work was 8 - 10 time greater in the silica-cement mortar than in the normal cement mort

Example 11.

Grout of mortar.

A mortar with sand particles up to 4 mm was prepared in order t evaluate the possibility of preparing easily flowable coherent grou with a large content of rather coarse sand and to demonstrate mixing sequence well adapted -for prefab rication of grout material in a form in which only water is to be added on the job . Th components used in the mortar were very similar to those used i Example 9, Mix No . 1, the amount of Mighty and the water conten being slightly higher. The mixing equipment was the same as i

Example 9. In the mix, the following components were used:

Quartz sand 1 - 4 mm 2763 g

0.25 - 1 mm 1380 g

- 0 - 0.25 mm 693 g

White Portland Cement 2706 g

Silica dust 645 g

Water 600 g

Mighty (dry powder) 120 g

Mixing.

15 -minutes dry mixing o cement + silic .+- sand +_ dry Mighty pow- ... der. Then, addition of 500 g of water and- mixing for 5 minutes . Thereafter, addition of 100 g water and mixing for 5 minutes . The consistency .of, the mix..after .addition_--o£--50Q-g -water-.-and. 3 minutes was, as assessed visually, very similar to the one in Example 9, Mix No . 1 , which contained the same amount of water (in spite of the altered mixing sequence) . The consistency after adding addi- tionaϋy 100 g of water was very soft. The soft mortar was poured into a 2.5 meter narrow plastic hose (internal diameter 18 mm) arranged in U-shape, the ends of the U pointing upward having a length of about 90 cm. The mortar was introduced in the U-shaped plastic hose by pouring into the hose through a funnel with a shaft of 17 cm length and internal diameter 12 mm . To avoid blocking at the narrow opening of the funnel (the diameter being only 3 times the diameter of the largest particles) , a steel rod of diameter 6 mm was moved up and down in the funnel opening. The mortar flowed easily as a medium- viscous liquid, completely filling the hose . The mass actually rose slightly higher in the free end of the hose than in the filling end,- probably due to a certain pumping action of the rod.

Comments on the results .

The experiment demonstrates the possibility of pumping a grout containing a large amount of coarser sand as a fluid coherent mass . Furthermore, the possibility of premising dry matter, including the dispersing agent, was demonstrated.

- CFREX!Γ

OMPI ΦfiξN T