POROUS GRANULES

The present invention relates to the dry matter composition of concrete or mortar that con- tains granules, and to the concrete or mortar manufactured from such a composition.

The raw materials, manufacturing technique, and logistics of concrete involve a lot of uncertainty factors, which are corrected by so-called safety factors. In addition to these, uncertainties related to the strength of materials, which are mainly the result of external factors, have an impact. These necessitate increases in concrete structures, concrete and the amount of steel.

A commonly used way of making so-called ready-mix concrete is to transport the raw materials to a separate mixing plant and to further transfer the mixed concrete to its application. Problems are created because of the bulky nature of concrete and the resulting inho- mogeneity of concrete. The logistics add to this uncertainty concerning the homogeneity of concrete.

The object of the present invention is to reduce the uncertainty factors and variations in quality related to the manufacture of concrete.

In particular, the object of the present invention is to manufacture a dry matter mixture that is suitable for the manufacture of concrete or mortar and that contains all the different dry substances in correct proportions with each other and attached to each other, which dry matter mixture can simply be mixed with water into a homogeneous mass.

The present invention thus relates to the dry matter composition of concrete or mortar that contains porous core particles, to the surface of which the particles of a hydraulic binder are attached, separate particles of the hydraulic binder, and a dry aggregate, to the surface of which the other constituents of the concrete or mortar are attached.

More precisely, the composition according to the present invention is characterized by what is stated in Claim 1. The concrete or mortar according to the invention, in turn, is characterized by what is stated in Claim 14.

An advantage of the present invention is that the dry matter composition can be transported directly to the destination of casting by ordinary container equipment and it will not harden prematurely, for example, during transportation. The porous granules included in the invention are capable of binding water, whereby the water that is needed in concrete curing is obtained to the concrete product by means of the same. The method according to the invention also decreases the safety factor. At the same time, the applicability of the manufactured concrete to industrial construction is improved. Furthermore, the use of the porous granule according to the invention minimizes the need of hydraulic binder per cubic metre of concrete. Similarly, the cost-effectiveness is increased by shortening the production times.

These advantages are achieved by manufacturing the concrete from subcomponents that are in correct proportions to each other. The present invention thus relates to the dry matter composition that is suitable for the manufacture of concrete or mortar and that contains porous core particles, to the surface of which the particles of a hydraulic binder are attached, and of separate particles of the hydraulic binder; the core particles consisting of an inert or pozzolanic material and forming porous granules together with the binder attached thereto; the granules, in turn, being at- tached to the surface of the dry aggregate.

According to a preferred embodiment of the invention, an adhesive is used to strengthen the attachment of the particles to each other, the adhesive preferably consisting of the nanoparticles of calcium carbonate or polymer particles, and preferably being a combination of carrier particles and polymer particles. According to a particularly preferred embodiment, the dry matter composition according to the invention contains particles of dry aggregate, on the surfaces of which there are nanoparticles of calcium carbonate (CaC0 ₃ ) and granules, the granules, in turn, containing inert or pozzolanic core particles that are coated with the hydraulic binder, the granules being glued to the dry aggregate particles (and the hydraulic binder) with the said adhesive. Granules

Said granules are porous, spherical particles, which are formed from the inert or pozzolanic material, which is preferably metakaolin, more preferably in the form of metakaolin particles (MK). The small particles of the hydraulic binder, which typically have sizes less than 3 um, are attached to the outer surfaces of these metakaolin particles. When necessary, these particles of the hydraulic binder can be treated so that their size distribution becomes sharper than ordinary.

According to a preferred embodiment of the invention, the inert or pozzolanic material is pozzolanic metakaolin, which is formed by agglomerating kaolin and by thereafter calcin- ing at least the outer surfaces of the agglomerates thus formed, and which most preferably is in the form of porous, spherical metakaolin sinter particles (MKS). These MKS particles preferably have sizes of 10 - 100 μτη, the main part of which, however, are in the order of 20 - 60 um. The small particles of the hydraulic binder with a size smaller than 5 um, however, mainly smaller than 3 um, especially smaller than 2 um, are attached to the sur- face of the MKS by means of condensation water or the said adhesive. At the forming stage, Ca(OH) ₂ and a CO? gas filler remain in the porous structure of the particles.

In connection with the manufacture, calcium oxide (CaO) and, possibly, sodium oxide (Na ₂ 0), and gas that most suitably is carbon dioxide, helium or air or a combination thereof, generally remain in the pores of the porous granules. In connection with the manufacture, nanoparticles of calcium carbonate remain in the porous structure of the MKS, which nanoparticles in connection with calcination partly decompose into calcium oxide (CaO) and carbon dioxide (C0 ₂ ). The porous structure thus preferably comprises 2 - 20% calcium oxide (CaO) of the total weight of the granule, more preferably 8 - 15%. Correspondingly, the porous structure preferably comprises 0.5 - 5% sodium oxide (Na ₂ 0) of the total weight of the granule, more preferably 1 - 2%, which is similarly formed from sodium hydroxide (NaOH).

CaO forms with water calcium hydroxide (Ca(OH) ₂ ), which further reacts pozzolanically with metakaolin. By means of the Ca(OH) ₂ that is produced by the MKS itself and the Ca(OH) ₂ that is produced by Portland cement, the pozzolanic reactions suitable for the purpose as well as the amount required by the same are achieved. This can be used to increase the early strength, for example. Sodium oxide (Na ₂ 0), in turn, improves the fire resistance of the composition.

When manufacturing MKS, C0 ₂ is generated in its porous structure, reacting with Ca(OH) ₂ , when concrete is being made. From the reaction, nanoparticles of CaC0 ₃ are formed, which further function as nucleation centres.

The method is used for influencing the ductility of the mixture, which is formed by the hydraulic binder, in mixing and casting the concrete, whereby a hydraulic binder that contains a larger amount of small particles can be used. This can be used for influencing the early strength. Particles of the hydraulic binder larger than 3 μτη remain free and their amount in relation to MKS particles is about the same; therefore, the probability distribution in the same space is 50%. The MKS particles also bind water in the composition, whereby the moisture in the composition is distributed more evenly than in known compositions, and the preferable moisture content remains longer in the composition and the con- crete or mortar made from the same.

The relation between these two groups of particles (MKS and the hydraulic binder) is stabilized, when they are further attached to the dry aggregate particles.

Dry aggregate

The dry aggregate used in the invention is preferably limestone, some other stone, silicon dioxide, synthetic dry aggregate or a mixture thereof, most suitably limestone, and it preferably has a particle size of 16 mm at the most, more preferably 0.1 - 16 mm, most suitably 0.3 - 6 mm. The above-mentioned granules and the large particles of >3 μιη of the hydraulic binder are attached to the surface of these dry aggregate particles by means of the adhesive. In this way, a paste, that is mortar, suitable for the manufacture of concrete is provided. Adhesive

The adhesive in the dry composition preferably comprises this combination:

1. a carrier,

to which

2. polymers

are attached.

The carrier preferably comprises nanoparticles of calcium carbonate (CaC0 ₃ ), which preferably have particle sizes of 50 - 1000 nm, most preferably 100 - 200 nm. They function for example, as growers (-220000 m ² / concrete m ³ ) of the bursting surface and as nuclea- tion centres in the hydraulic binder stone. They contain 1 - 15%, most preferably 10% of generally useful metallic impurities.

The polymers, in turn, are preferably copolymers, the base polymers of which are polyatomic carboxylic acids with linear shapes, which because of their positive net charges are capable of attaching to carbonates. According to a preferred embodiment, combination particles are formed from this combination, wherein polymer branches are accumulated around nanoparticles. The combination particles have a coverage area (that is, the diameter of nanoparticle coated with polymer) of about 100 nm - about 1000 nm, preferably about 200 nm - about 400 nm, most suitably about 200 nm. These combination particles form a sticky, dry film between the particles of the dry composition that are to be attached to each other, or between the granule and the particle.

Hydraulic binder

The hydraulic binder is preferably Portland cement (OPC) or cement that is particularly rich in C2S (dicalcium silicate), most preferably Portland cement. As mentioned above, the particles of the hydraulic binder can be treated, as required, so that their size distribution becomes sharper than the ordinary. Typically, the particle size distribution of Portland cement is quite low and it provides a reasonable castability in ordinary concrete. Making the size distribution sharper and the resulting improvement of the form factor are carried out so that Portland cement is treated in a pressure roller that crushes part of the large cement particles. This improves the form factor of the particles and increases the amount of small particles by 10 - 15%. In the method according to the invention, more particles of < 3 μπι can be used than in the known technique without an increase in the amount of water.

Copolymer

According to a preferred embodiment, in addition to the above-mentioned gluing, the invention uses polymer in increasing the coverage areas of the various particles of the gran- ules. These polymers also function as plasticizers and adjusters of the movement of water in solutions.

The polymers used are preferably copolymers, the base polymer of which has a molecular shape that is a linear and polyvalent carboxylic acid. The molecular weight of the base polymer is preferably 2000 - 4000 g/mol, more preferably about 4000 g/mol, and its de- gree of polymerization 55. The base polymer is most preferably acrylic acid.

The copolymers are preferably formed using, in addition to the base polymer, poly- ethylenglycol and maleic acid as monomers. When acrylic acid is used as base polymer, esters of polyacrylic acid and cross-linked acids are thus formed. The monomers and structures in question are:

Acrylic acid HiC = CH · COOH

Polyethylenglycol HOCH ₂ · (H ₂ C · O · CH ₂ ) _n · CH ₂ OH

Maleic acid HOOC · HC = CH · COOH

The polymerized product thus obtained is acidic. Its pH is within 1.7 - 2.5. For use, the product is neutralized, however, preferably using 20% NaOH to a value of pH 6. CH ₂ CH C ^/ * NaOH→ CH ₂ · CH · Λ H ₂ 0

P ^A OH ^{Na Salt} ONa

When emulsion polymerization is used, many different polymers are obtained. In HPLC studies, different sizes of polyethylenglycol acrylates, polyethylenglycol ethers and crown ethers and unreacted monomers can be discovered. Darkening in light refers to the fact that the mixture still contains unreacted double bonds in the polymers and monomers.

The attachment of acrylic acid copolymers to mineral particles takes place when the anionic carboxylate of the polyacrylate influences the positive groups of the minerals, whereby an insoluble soap is formed. On an average, the polymer chain contains one ani- onic group per each linked monomer, which may mean that within the range of one nanometre, the base polymer comprises about ten anionic carboxylate groups ready to attach to the surface of any particle of the dry composition. The attachment takes place the easiest to the calcium of the crystalline calcium carbonate and the iron that exists as an impurity, the metakaolin cinter and aluminium of the hydraulic binder. Soluble calcium, iron and alu- minium ions also precipitate the polyacrylate as insoluble soaps, which have a lubricating effect.

When dried, the copolymers that are suitable for the invention form a film soluble in water, when the drying temperature is below 100 °C, preferably about 50 °C, and a film insoluble in water, when the drying temperature is above 100 °C, preferably about 110 °C. When combining the polymer and a carrier (calcium carbonate), a multiple effect is obtained. The combination works as a plasticizer, controller of the movement of water, and an adhesive film soluble in water.

The polymer as such is a combination, wherein the base polymer defines the length of the copolymer, and the other monomers complement the different coverage areas of the base polymer. The carrier, in turn, increases the coverage area of the polymers and functions as an independent strengthener of the binder hydrate.

End product

The dry composition according to the invention contains all the dry ingredients needed for the manufacture of concrete or mortar in a well-mixed form, whereby merely adding water and mixing the composition conventionally converts the composition into a homogeneous concrete or mortar that is strong and wherein the number of errors (such as cracks and irregularities) are minimized. The number of manufacturing stages is thus also minimized, when the product in its entirety is produced by the manufacturer, where the curing is also mainly ensured.

The dry composition preferably contains dry aggregate particles, on the surfaces of which there are nanoparticles of calcium carbonate (CaC0 ₃ ), hydraulic binder and granules; the granules, in turn, possibly containing an adhesive and inert or pozzolanic core particles, which are coated with the hydraulic binder, the granules being glued to the aggregate parti- cles (and the hydraulic binder) with the said adhesive.

Examples

Example 1 - Use of the mixture of copolymer and carrier

The use of copolymer that was based on acrylic acid together with a carrier as a plasticizer was successfully tested by mixing together, as aqueous slurries of 20%, 92.5 weight-% of the nanoparticles of calcium carbonate and 7.5 weight-% of the polymer mixture. Plasticiz- ing of concrete was sufficient on a small dosage, 800 g per m ³ of concrete.

Tests were also conducted on a plasticizer that was dried at a low temperature (t = 50 °C), whereby the plasticizing effect on concrete was effective enough after redissolution. The temperature is not adequate to cause a further polymerization reaction in the mixture, whereby the mixture maintains its solubility in water.

The mixture of polymer and CaC0 ₃ thus obtained was subjected to gluing tests by heating it in an oven at 110 °C. After the water had evaporated, a dense film insoluble in water was then formed, effectively gluing the particles together. The film was completely clear, referring to the fact that under the effect of heating, the unsaturated components of the polymer mixture reacted with each other and a final reaction took place, cross-linking the linear base polymers into a larger molecule. The properties of the mixture of polymer and carrier (particularly its solubility in water) were studied by means of these two tests:

Test 1.

CaC0 ₃ + copolymer were dried into a film, so that the temperature of the combination did not exceed 50 °C. Dissolving of the film, 95%, took place during 5 minutes at a tempera- ture of 20 °C, the rest during 10 minutes. No measurable difference caused by the drying could be perceived when plasticizing.

Test 2.

CaC0 ₃ + copolymer were dried into a film, so that the temperature of the combination increased 110 °C. The film did not dissolve in water. Example 2 - Manufacture of dry composition Dry test compositions were prepared as follows:

DA was washed;

CaC0 ₃ + copolymer were added, 30%;

dry powder of the granule was added; and

drying was carried out in fluid form, so that the temperature of the product did not exceed 50 °C.

The dry compositions were mixed into concrete for a concrete test, wherein the same ratios between components were used as in the following experimental compositions. The compression strength (after 6 h at 50 °C, with a test cylinder of 0 70 mm, h = 70 mm) and spreading (at the Hagelman table) were measured. Experimental compositions were prepared (Tests 1—4), the amounts used being exemplary. The mutual ratios of the ingredients used in these experimental compositions were stated as working particularly well in the invention, however.

Test 1

Concrete per m ³

Dry aggregate (DA) 1980 kg

Granule

MKS 60 kg

OPC < 2 um 50 kg

CaC0 ₃ + copolymer 11 kg

Total 2301 kg

In the concrete test, the measured compression strength of this composition was 30 MPa and the spreading 180 mm.

Test 2.

1. Granule

Concrete per m ^:

MKS 60 kg

OPC < 2 um 50 kg

OPC > 2 um 200 kg

310 kg

2. Paste

Granule 310 kg

CaC0 ₃ + copolymer 11 kg

Water:

w/c 0.4 ^a 100 kg

Pozzolan ^b 10 kg

Absorption water ^c 60 kg→ 170 kg

491 kg a: w/c 0.4 is hydration water for the hydraulic binder, and the marking w/c used refers to the w/c ratio (= water-binder ratio), the target value of which is about 0.4.

b: Pozzolan water is the water needed for the pozzolanic reaction,

c: Absorption water, in turn, is needed for the water absorption of MKS.

In the concrete test, the measured compression strength of this composition was 26 MPa and the spreading 152 mm. Test 3.

Agglomerated, calcined MKS + CaO and/or Na ₂ 0 were prepared:

1. These slurries into the spray drier:

1. Kaolin 1000 kg 2. Kaolin 1000 kg

CaC0 _3n 100 kg CaC0 _3n 20 kg

Copolymer 20 kg Copolymer 2 kg

Water 1100 kg NaOH 20 kg

Water 1000 kg

The intermediate products obtained were kaolin agglomerates of 10 - 100 |im (20 - 40 urn).

2. Calcination:

The intermediate products were heat-treated in a fluid (at 1000 °C), whereby strong sinters were obtained (metakaolin-% (MK- ) of 20 - 40).

Product 1 Product 2

MKS -1000 kg MKS - 1000 kg

MK - 200 - 400 kg MK - 20 kg

CaO - 50 kg Na ₂ 0 -16 kg

Products 1 and 2 are example products. For example, the amounts of CaC0 ₃ and NaOH may vary, where necessary. Test 4.

Products were prepared, containing the copolymer according to the invention:

1 . CaC0 _3n 0 100 - 300 nm (Fe content 10%)

2. The molecular weight of copolymer is 400, the degree of polymerization 55. The polymers were observed to increase the repulsion field by -50 nm outward from the surface of the particle.