EP2331476A1

EP2331476A1 - Structured binding agent composition

Info

Publication number: EP2331476A1
Application number: EP09749160A
Authority: EP
Inventors: Pentti Virtanen
Original assignee: Kautar Oy
Current assignee: Kautar Oy
Priority date: 2008-10-01
Filing date: 2009-09-28
Publication date: 2011-06-15
Also published as: RU2011114905A; FI20085927A; FI123552B; WO2010037903A1; RU2526920C2; FI20085927A0

Abstract

The present invention concerns a grain composition for the manufacture of a concrete mass, consisting of granules, each of which contains filler particles, to the surface of which hydraulic binder particles have been attached. The invention also concerns a method as well as equipment for manufacturing the composition as well as a concrete or mortar mass, which contains said composition, and a method for manufacturing this concrete or mortar mass.

Description

Structured binding agent composition

The present invention relates to a structured, granular binder composition, which is suitable for manufacturing concrete mass, and to a concrete or mortar mass that contains the granular composition. The invention also relates to methods of manufacturing the granular composition and the concrete or mortar mass.

Concrete is a material that consists of various ingredients and the properties of which are constantly changing. A great deal of factors affects the behaviour and the properties of concrete, such as changes in the moisture and temperature, the carbon dioxide content of the air, etc. There is a strong dependence between the changes in the moisture content of concrete and its mechanical properties, such as its strength, shrinkage, creep and the elastic modulus. Water, i.e., moisture, is also an essential part of old and hardened concrete.

The active ingredient of concrete, i.e., the hardened binder or cement stone, consists of small components of varying shapes, which, in addition to chemical bonds, are mainly combined by physical close-range forces, and of small pores between these structural components, which are filled with water molecules. Such a porous and hygroscopic substance, which has an enormous amount of inner surface area (about 200 nrVg), is sensitive to external influences and experiences continuous structural changes.

Due to these structural changes that are caused by both the ambient temperature and moisture, the cement and the concrete made of it are substances which are difficult to define. However, the most general binders, such as cement, have a common property that they are curable with water, and such binders are called hydraulic binders. In this context, we refer to a granulated binder composition and the side and further processes of its hydration, to which the invention relates. The most typical of these hydraulic binders is Portland cement, the main components of which comprise tricalcium silicate (C₃S in terms of cement chemistry, 54%), dicalcium silicate (C₂S, 17%), tricalcium aluminate (C₃A, 10%) and tetracalcium aluminoferrite (C₄AF, 10%). In essence, the latter two are formers of clinker only and they do not have a great effect on the strength provided by the binder.

When hydrating, C₃S releases 3 moles OfCa(OH)₂ and C₂S releases one mole of calcium hydroxide, respectively. The fastest to harden is C₃A, which requires 6 moles of water for the hydration, as well as C₄AF. At the beginning, the compression strength of the binder mainly develops from the hydration of C₃S and, in the long run (>90 days), from the hydration of C₂S, by which the same end result is obtained as by the hydration product of C₃S, finally, within the same time, in about a year, at normal temperature. A theoretical ratio of water and cement (the w/c ratio), wherein all of the water would be consumed by hydration, would be 0.245 at the composition described above. Due to so-called gel water, of which there is about 18%, the practical water/cement ratio is however higher. Water has then penetrated into pores of about 2 nm. This water, which is slowly consumed by the hydration, causes a shrinkage in the concrete mass, similarly to the carbonisation of the released Ca(OH)₂.

When making concrete, it is also possible to achieve a bond strength by side reactions other than the reaction of the so-called clinker minerals and water. When a silicate mineral reacts with lime and water, i.e., it binds the lime instead of releasing it, as is the case in C₃S and C₂S reactions: this is called a pozzolanic reaction. In principle, the pozzolanic reaction is a reaction of calcium hydroxide [(CH) in terms of cement chemistry], silica, SiO₂ (S) and water (H), wherein a CSH compound as well as CAH and CASH compounds are formed, depending on the pozzolanic material. When kaolin is heat-treated at a temperature of 500-850 C°, it loses its crystal water and Al₂O₃ • SiO₂, which is pozzolanically active in water, is obtained. The product is called metakaolin. Various companies sell metakaolin and research shows that it is more effective in improving the strength than microsilica whilst, at the same time, being more effective in compacting the concrete, etc.

Earlier, the Ash Grove Cement Company has patented, by the patent US 5,788,762, the use of metakaolin as pozzolan among cement so that, after combustion, the metakaolin is ground to the degree that the ratio of water and binder to be worked is less than or equal to 0.33. This means that the metakaolin cannot be ground any further, since the need for water increases considerably.

In addition to the above-mentioned ways of accomplishing bond strength, a third way of accomplishing bond strength in a mineral binder is to allow small particles to combine into larger ones through crystallisation. This Gibbs law ∑ajg; -→ into a minimum, wherein a; is the surface area of the particles and gj is the surface energy of the particle surface, thus means that small particles always attempt to grow larger, and further, the smaller the particles, the faster the growth.

One problem in making concrete has been the mixing technique, wherein the purpose is to make a homogeneous mixture of fine binder particles and rough aggregate. The binder particles are then easily glued to each other, forming agglomerates, which impair the quality of the concrete.

The core of the problem is that the fine ingredients require 1-6 kWh/t of mixing energy, whilst the rough fractions require 0.3-0.5 kWh/t.

The apparatuses, which over 1-2 minutes effectively mix the fines by the required effect, require more power than what is needed for mixing the whole concrete. Therefore, a type of compromise has been applied to concrete mixing, which however, is used at the cost of the quality of the product.

The object of the present invention is to provide a composition, which is suited to the manufacture of concrete or mortar mass and which simultaneously utilises various mechanisms that add strength to the concrete, in a manner which enables the mixing to be kept simple.

Surprisingly, it has been observed that a high strength can be achieved by using binder granules that are formed in advance (before manufacturing the concrete), whereby the surface energy of the various components of the composition can be reduced.

Thus, the present invention relates to a granular composition for the manufacture of concrete mass and the concrete or mortar mass that is manufactured from the same.

More precisely, the composition according to the present invention is characterised by what is stated in the characterising part of Claim 1.

The method for manufacturing the composition according to the invention, in turn, is characterised by what is presented in Claim 9, the concrete or mortar mass according to the invention is characterised by what is presented in Claim 14 and the method for manufacturing concrete or mortar mass is characterised by what is presented in Claim 16.

Furthermore, the equipment according to the invention for manufacturing the grain composition is characterised by what is presented in Claim 18.

Granules contain a lot of pores, which bind and absorb water by their capillary forces within a given time, whereby this water can be used for the hydration of the hydraulic binder components later on. At the same time, the virtual ratio of water and cement during mixing and concrete casting is relatively high, whereby the mass is easy to cast, yet it stiffens fairly quickly in the mould. The Ca(OH)₂ that was formed in the hydration immediately forms extra precipitable CaCO₃, if the kaolin is calcined by flue gases or otherwise in a carbon dioxide atmosphere. The Gibbs equation (∑ajgi — > minimum) also explains why the precipitable substances always precipitate on the surface of another particle. The minimisation takes place quicker, when the point of contact is not counted as a surface that is formed.

By means of the present invention, the fines of the concrete can be moved to the mortar portion of the concrete, so that a homogeneous binder portion is formed. This is carried out by bringing, into the aggregate, pre-mixed fines in a correct proportion and as fairly large granules, and not in a ground form, as in the Ash Grove Cement Company patent, whereby the need of mixing water does not increase a great deal because of the large amount of fines, and the viscosity of the mass does not become high. In this way, the nature of concrete mixing changes into homogeneous mixing between these granules and the aggregate, whereby a power of mixing of 0.3 kWh/t is adequate.

The effects of the invention are quite extensive. Among others, it can be used to provide, by the modern-type mixing equipment of concrete mixing plants, both a homogeneous mixing of the concrete fines and a successful placement of nano-size calcium carbonate particles between the hydraulic binder particles, whereby they influence the structure of the hydrate thus generated, giving it new properties, such as an increase in strength and toughness, and accelerating the hardening of the hydrate. Fig. 1 shows equipment that is suitable for manufacturing a preferred grain composition according to the present invention.

Fig. 2 is a drawing, which shows the external forms of the granules on a 240-fold enlargement, when manufactured in different ways; as a fluid in Fig 2a and as a non-fluid in Figs. 2b, 2c and 2d, whereby the fluid refers to metakaolin agglomerates that are coated in a gas flow, and the non-fluid refers to those mixed when dry.

Fig. 3 shows electron microscope images of the metakaolin granules according to the invention; Fig. 3a shows a 250-fold enlargement and Fig. 3b shows a 4000-fold enlargement.

The present invention thus relates to a grain composition for the manufacture of concrete mass, consisting of granules, each of which contains filler particles, to the surface of which hydraulic binder particles are attached.

The invention also refers to a concrete or mortar mass, which, in addition to this grain composition, contains fine and coarse aggregates.

According to a preferred embodiment, concrete consists of a mortar portion, i.e., binder portion, and an aggregate portion, whereby the binder portion preferably comprises the following ingredients:

- hydraulic binder, such as Portland cement (OPC), which preferably contains C₃A and C₄AF portions; - filler, which preferably comprises limestone or SiO₂ stone;

- pozzolanic binder, which preferably comprises metakaolin sinter (MKS), wherein the pozzolanically reactive portion comprises metakaolin, of which there is 10— 80% in the sinter;

- calcium carbonate as nano-size particles (CaCO₃nano); - plasticizing agent, which typically is a polymer of acrylic acid; and

- water, which preferably is normal industrial water or treated water [which contains, e.g., Ca(OH)₂ + 2CO₂ → Ca(HCO₃)₂], the aggregate preferably comprising the following ingredients:

- fine aggregate (with an average particle size of < 6 mm, preferably < 4 mm, more preferably < 2 mm), which is preferably limestone, more preferably form-crushed limestone, or SiO₂ stone; more preferably in the form of crushed aggregate or natural stone; and

- coarse aggregate (with an average particle size of 4-16 mm, the largest particles up to 32 mm), which preferably comprises crushed SiO₂ aggregate, natural SiO₂ stone, crushed limestone aggregate or so-called gangue from limestone mining.

According to a preferred embodiment, the aggregate comprises 50-85 % by weight of fine aggregate, more preferably 70-75 % by weight, and 15-50 % by weight of coarse aggregate, more preferably 25-30 % by weight.

It is common knowledge that limestone in concrete even repairs its cracks, since CaCO₃ is slightly soluble in water (this is how the stalagmites in caves are formed). Limestone as the aggregate of concrete gives the concrete a compression strength, which is at least the same as, preferably higher than the one obtained by granite aggregate.

The fine stone aggregate that is used in the invention, i.e., the "filling agent" or "filler" is preferably limestone, as both the concretion of carbonates and the so-called solid solution between CaCO₃ and Ca(OH)₂ can be implemented by it (Lea, The chemistry of cement and concrete, Third edition, 1970, page 266.). Tricalcium aluminate hydrate also forms quickly. This limestone can preferably be mixed with the "granule" in an amount of 2-30 % of the entire weight of the granule, most preferably about 15 %.

According to a preferred embodiment of the invention, this limestone component is brought into the filler granule at least partly on a so-called nano-scale, as in a suitable environment, particularly, the nano-scale particles tend to grow the quickest. Generally, the growing, re-crystallising particles attach to the surfaces of other particles by mechanical forces and so-called van der Waals vicinity forces. In addition, calcium carbonate nanoparticles also have the property that they facilitate the processibility of the concrete mass. The pozzolanic binder is preferably calcined clay that contains kaolinite or kaolin, part of which comprises metakaolin.

The pozzolanic binder especially preferably comprises metakaolin sinter (MKS), which contains metakaolin, preferably 20-65 % by weight, kaolin, preferably 75-30 % by weight and calcium oxide (CaO), preferably 5-20 % by weight. Before adding into the other ingredients of the composition, it can preferably be coated with the particles of a hydraulic binder by most suitably using 30-120 % of hydraulic binder of the weight of the pozzolanic binder.

The ratio of the hydraulic binder, which excretes calcium hydroxide in the hydration, and the pozzolanic binder is of a type, wherein the pozzolanic binder binds no more than 90 % of the calcium hydroxide that is released.

Typically, the plasticizers can comprise polyacrylamide, polyacrylate, polycarboxylate, lignosulphonate, naphthalene sulphonate or melamine sulphonate or several of these, most preferably their polymers.

When the dispersing agents, which are placed on the surface of the granule, are added to the binder granule, a product is obtained, which comprises only the binder granules, aggregate stone and water that are to be measured at the concrete mixing plant.

The granules of the granular composition preferably contain

- hydraulic binder; - pozzolanic binder that is agglomerated in advance;

- fine aggregate, preferably fine-ground calcium carbonate, most suitably the nanoparticles of calcium carbonate;

- plasticizer; and

- a small amount of water.

According to the present invention, before mixing the concrete, the components of the concrete are grouped in a new manner by forming granules according to any of the following alternatives: Granule 1 :

Core components are formed from the filler particles, and the calcium carbonate particles, to the surface of which the plasticizer is attached, are first added amongst these core components and, thereafter, the hydraulic binder.

Granule 2:

A granule is formed from the filler and the hydraulic binder, mainly comprising the core component that is formed from the filler particles, the plasticizer being attached to the surface of the core component and the particles of the hydraulic binder being attached around it. Calcium carbonate particles (with a size of < 800 nm) are then attached to this granule.

Granule 3 (a special case of Granule 2): A granule is formed from limestone filler and the hydraulic binder, mainly comprising a core component made of the limestone filler, the plasticizer being attached to the surface of the core component and the binder particles being attached to this core component by means of the metaproduct Al(OH)₃ of the binder C₃A and the hydration product of the limestone.

The concrete, in turn, is preferably mixed by adding the following ingredients in the said sequence:

1. granule

2. water or treated water containing Ca(HCOs)₂, the amount of which in the treated water is preferably about 10 g/1

3. fine aggregate

4. coarse aggregate

5. (metakaolin sinter)

At the beginning of mixing, plenty of water is used, as the fine aggregate of the binder composition is attached to the surface of the microfiller. In this way, the fine and coarse aggregates can be well- watered. At a later stage of mixing, water detaches the binder particles from the surface of the microfiller and energises the plasticizer that was in a dry state, and its carriers (calcium carbonate or filler). The plasticizer and the carrier compensate for the water bound by the binder and keep the concrete easy to process.

The binder system, i.e. grain composition, of the present invention can be varied for various purposes. Metakaolin can be replaced or supplemented with silica and the cement with aluminous cement, etc. The idea of the invention is that all functional components are collected in one granule. The granules are easy to mix with the aggregate substance and water into a more homogeneous mixture and the mixture is easy to dose in the manufacture of concrete. The manufacturer of concrete only needs to by the "granule" for a certain purpose and only one silo is needed for the binder.

According to a preferred embodiment, the pozzolanic binder is suitably rendered the desired form by first agglomerating the kaolin, e.g., by spray drying, and not calcining until after this into metakaolin, preferably by hot flue gases. To make the granule after this, the metakaolin sinter (MKS) it brought into contact with a desired hydraulic binder, preferably so that a dispersing agent is present and, finally, said structured two-component agglomerate is coated, e.g., in a gas flow by fine calcium carbonate powder, preferably so- called nanoparticle calcium carbonate (n-PCC), which is manufactured by precipitating.

According to another embodiment, the pozzolanic binder, such as clay that contains kaolin, is first mixed with water and, optionally, an additive, preferably an inorganic substance, is added into the water to reach a dry matter content of 30-70 %; the slurry is dried in the gas flow and further calcined, at least on its surface, in a gas flow of 500-850 °C by methods known as such, but preferably in a gas flow that contains carbon dioxide. To make the granule, a suitable amount of concrete plasticizer is sprayed onto the surface of the calcined and cooled metakaolin agglomerate to bind the cement particles to the surface of the agglomerate, when cement dust and the agglomerates are brought into contact with each other. It should be noted that the cement dust and metakaolin adhere to each other by van der Waals forces even without the concrete plasticizer. In connection with the studies of the invention, it was observed that metakaolin collected other particles on its surface.

At the following stage, CaCO₃ nanoparticles and ground limestone are blown into the flow of powder. In a third embodiment, the binder granule is manufactured directly, so that the metakaolin agglomerate that is manufactured according to the above and the hydraulic binder and the limestone filler are brought together in a dusty form (a fluid) and the particles are allowed to stabilize, e.g., in a fluidised bed over 10-60 sec and, after this, precipitated calcium carbonate slurry is sprayed amongst these ingredients together with the plasticizer. In that case, an amount of water, which corresponds to a maximum of 5-10 % of the chemical need of water of the hydraulic binder, is added into the mixture with the precipitated calcium carbonate.

According to a fourth embodiment, the other powders are mixed with each other in a dry form and, finally, the finished metakaolin agglomerates are mixed therewith, collecting the other particles on their surfaces.

The patent US 6,027,561 of the Engelhard Corporation describes a method of forming metakaolin agglomerates, which essentially deviates from the present method, wherein the agglomerates are formed in an aqueous solution before calcination and which ensures that the agglomerate (in the calcination) obtains a strong structure. At the same time, energy is saved.

The strength of the structure can be further improved by mixing a water-soluble inorganic compound with the mixing water, e.g., the mixing water of spray drying, which inorganic ingredient dries and binds more particles to each other. Such a water-soluble substance is preferably liquid glass which, after drying, dissolves in boiling water only. Gypsum can be used for the same purpose, or the soluble organic salts of calcium, such as formiate or acetate, in which cases the organic portion burns out in the calcination. This formation of agglomerate before calcination or partial calcination is dealt with, among others, in our previous patent application US 20050000393.

The cement particles in the granules have average diameters of about 12 μm. Correspondingly, the average diameter of the nanoparticles is 50-800 nm, preferably 100- 500 nm, most preferably 100-200 nm, and the average diameter of the microfiller is < 100 μm, preferably 10-40 μm. These components can be used to form a granule, the average diameter of which is < 300 μm, preferably 20-60 μm, most preferably 20-40 μm. According to an especially preferred embodiment of the invention, the grain composition is manufactured so that the projection areas of the hydraulic binder and the calcium carbonate particles become as large as or smaller than the areas of the filler particles of the granules.

The outermost layer of the granule surface preferably mainly consists of cement particles, wherein the C₃A has slightly reacted after drying. After the formation, gas remains in the granule, which gas is air, helium or carbon dioxide, depending on the way of formation. The amount of gas is 0.8—1.2 dm³/ kg of granule.

The attachment of the cement particles to the surfaces of the filler particles (such as limestone particles) takes place by utilising the quick hydration of the C₃A of the binder granule. This hydration time remains constant for 6 min - Ih, even 2 min - Ih. In that case, the filler particles, the surface of which is watered, together with the metastable product Al(OH)₂ of the C₃A of the binder particles form a hydrate, which binds the binder particle to the surface of the filler particle. By drying the product thus generated, a granule is obtained, which can preferably be blended as binder with the concrete. The hydration of the filler/binder granule continues in the concrete, when water is included. The quick hydration of the granule thus produced is surprising; being quicker than if the different components of the binder composition are added separately into the concrete.

The CaCO₃ nanoparticles contained in the granules improve the processibility and, through that, reduce the need of water in the processing, further reducing the formation of so-called capillary pores, thus adding to the frost, fire and corrosion resistances of the concrete.

The plasticity can be adjusted by the invention by adding into the concrete, at the end stage of mixing (however, before casting the concrete), metakaolin sinter powder, which absorbs the water that moves in the mixing, thus working as a water supply in the progress of the hydration.

Adding the filler and the hydraulic binder in one granule to the concrete mixing influences the amount of mortar portion required and, in this way, a greater amount of filler can be used without growing the water to binder (w/c) ratio. The purpose of using the filler is to influence this w/c ratio, the target value of which is 0.4:

w w c c,._ed + kF

wherein: w is the amount of water, c is the amount of cement, c_re(i is the amount of cement, wherein the effect of the amount of filler is taken into consideration, F is the amount of filler and k is the coefficient, which indicates the effect of the filler amount on the amounts of cement and water (wherein the amounts are given as weights). The target value of the coefficient k is 0.25.

The target value is fulfilled, e.g., in a case, in which:

w 100 kg 100% - = = 0.4

C 200 kg + 0.25 x 200% 250%

This ratio, in particular the c value that corresponds to the cement, can be influenced, among others, by adjusting the amount of binder, the mutual ratios of the hydrate and the filler, and their amounts, ability to mix and processibility. By adjusting the other amounts and ratios, savings can also be made in the amount of cement, i.e., the binder.

When the w/c ratio mentioned above is as desired, i.e., its value is 0.4, the space between the particles of the hydraulic binder has a diameter of about 700 nm. The nanoparticles of calcium carbonate must fit in this space, where they partly hydrate and reduce the volume, which in the concrete of prior art is filled with water. Therefore, the nanoparticles preferably have average diameters of < 200 nm. When treated with plasticizer, these nanoparticles plasticize the binder composition.

Drying shrinkage is a common problem with concrete, impeding the quality of the final concrete. It is caused by the gel water and the capillary water that remain between the particles in the concrete. A general value of drying shrinkage is 0.6 %o. To eliminate the disadvantages caused by the drying shrinkage on the quality of the concrete, the drying shrinkage should however be lower than the breaking stretch of concrete, which generally is about 0.2-0.3 %o. In the present invention, the drying shrinkage is reduced by introducing, between the coarse particles of the concrete, finer particles, such as microfiller along with the granules.

The granules, which remain between the aggregate particles of the concrete and contain the limestone filler and the hydraulic binder, increase the volume filled with the binder composition between the aggregate particles. When the binder hardens, this reduces the deformations of the hydrate thus formed, which cause the drying shrinkage mentioned above, among others.

The size of the space between the aggregate influences the amount of microfiller needed and its particle size, and the size of the space is further influenced by the particle size of the aggregate. Due to this, preferable filler is the one, which has particles with an average diameter of 10-40 μm.

When manufacturing a preferred paste composition, the amounts of ingredients added can be as follows:

% by weight Typical example Size

Hydraulic binder 30-50 250 kg 2-100 μm

Filler 20-40 200 kg 0.1-100 μm

Water 10-20 100 kg

Calcium carbonate 1-5 20 kg 2-1000 nm

MKS 3-5 38 kg (or up to 60 kg) 10-100 μm

(Plasticizer 0.1-0.5 2 kg (or 0.8 kg only))

More preferably, 20^4-0 % by weight of the hydraulic binder is separately added amongst the MKS, whereby it adheres to the surfaces of the sinter particles.

Most preferably, the composition is manufactured using amounts of substances, the mutual ratio of which essentially corresponds to any of the following composition examples: Composition 1 Composition 2

Granule:

MKS 60 kg

Limestone filler 230 kg

Hydraulic binder (<3mm) 50 kg 50 kg

For the paste, the following is admixed:

Hydraulic binder (>3mm) 200 kg

Water 170 kg 100 kg

To manufacture the mortar, fine aggregate is preferably added into the paste thus obtained in an amount of about 1000 kg in the case of the composition examples. Correspondingly, the concrete mass is mixed of the mortar by adding coarse aggregate in an amount of about 1000 kg in the case of the composition examples.

Water may also be carried to the composition as various hydration products or absorbed into the granules of the composition. Water is preferably added in suitable amounts as hydration water and for the hydraulic binder, the pozzolanic reaction and the absorption water of the MKS. It is assessed that, of the water used in the composition example 1, 100 kg is most suitably needed for the hydraulic binder, 10 kg for the pozzolanic reaction and 60 kg for the absorption water of the MKS.

The present invention also relates to equipment, by means of which the granules of the grain composition according to the invention can be manufactured. The said equipment preferably contains the following components (Fig. 1):

1 First container

2 Cyclone separator

3 Pressure roller

4 Opposed cylinder rotor distributor

5 Second container

6 Coating equipment

7 Mixing equipment

8 Storage tank According to this preferred embodiment, the equipment thus contains a first container 1, a cyclone separator 2, which is placed downstream of the first container 1, a pressure roller 3, which is attached to the bottom part of the cyclone separator 2, an opposed cylinder rotor distributor 4, which is correspondingly attached to the pressure roller 3, coating equipment 6, which is in contact with the upper part of the cyclone separator 2 and to which a second container 5 is attached, mixing equipment 7, which is placed downstream of the coating equipment 6, and a storage tank 8, which is placed downstream of the mixing equipment 7.

This granule formation equipment preferably functions so that the ingredient which is needed by the granule, such as the hydraulic binder, can be fed from the first container 1 into the cyclone separator 2. In this separator 2, fine particles are separated from coarse ones. The coarse particles with sizes of preferably > 15 μm are ground fine by feeding them through the bottom part of the separator 2, first through the pressure roller 3 and then the opposed cylinder rotor distributor 4, after which they are combined with the hydraulic binder that is conveyed from the first container 1, whereby the partly pulverised binder particle mixture thus formed is conveyed back to the cyclone separator 2. Pressure roller crushing can be used to reduce the relative size of the largest particles, whereby their size distribution becomes even. The fine particles, which are separated from the coarse ones in the cyclone separator 2 and which preferably have sizes of < 15 μm, are conveyed through the upper part of the separator 2 into connection which the coating equipment 6, where they are mixed with the feed that comes from the coating equipment 6 and preferably contains a microfiller, which is conveyed from the second container 5 and coated with calcium carbonate in the coating equipment 6, a plasticizer being attached to the calcium carbonate, and preferably with a feed that contains a pozzolanic binder. The substances thus coated are fed from the coating equipment 6 into the mixing equipment 7, where the microfiller calcium carbonate particles are mixed with the binder particles, after which the granules thus formed, are conveyed to the storage tank 8 to be stored before use.

According to a preferred embodiment of the invention, the equipment also contains calcination equipment, including a calcination furnace, which is in contact with the coating equipment 6 and the mixing equipment 7, and the pozzolanic binder can be rendered its desired form in the calcination equipment, i.e., it can preferably be agglomerated and calcined before combining with the other components of the granule. The concrete mass according to the invention contains, mixed together, the granular composition described above and stone aggregate and water.

The mass is manufactured by granulation from this grain composition, which contains at least the binder, an additive and fine aggregate in predefined proportions, after which said granules are mixed with stone aggregate and water.

The only requirement of the present invention that deviates from normal concrete mixing is that a mixer and mixing energy, which is more intensive than normally, are needed, not so much time-wise but rather regarding the effect and volume. The mixing is most suitably continuous.

The invention and its advantages are described by the following, non-limiting example.

Example

Kaolin was elutriated by first mixing it into an aqueous slurry of 55 %, then it was treated by a dispergator and was adjusted with a NaOH solution to a pH value of 7.5. A slurry was obtained, the viscosity of which at a temperature of 21°C was 520 cP. A saturated Ca(HC03)2_-a solution was added into the slurry, so that, when counted as CaCθ₃, the amount of dissolved carbonate was 1.8% of the amount of dry matter. This slurry was spray-dried and particles with a diameter of 11.4 μm were obtained, of which the d₉₀ was 9.9 μm. It was observed that the agglomerate particles thus formed were spherical and almost equal in size.

The calcination in this test took place in an electric resistance furnace manufactured by the Bentrup Company and in a calcined clay melting pot in 1.5 kg batches, so that the temperature was slowly raised from room temperature up to 1050°C, where it was kept for an hour. The mass defect totalled 12.61%, whereby it could be calculated that the kaolin content apparently was 88%. The granules according to the invention (Fig. 3) were manufactured by mixing the ingredients according to the following composition (Fig. 2, non-fluid) under dry conditions:

Metakaolin agglomerate 2CM-0 kg/m³ of concrete 10-100 μm

Portland cement 250 kg/m³ of concrete 2-100 μm

CaCO₃ nanoparticles 10-40 kg/m³ of concrete 2-500 μm

Microfiller 100 kg/m³ of concrete 0.1-100 μm

Plasticizer 2 kg/m³ of concrete

The nano PCC together with a small amount of water and with the water that came along with the plasticizer were first added into this composition. The total amount of water used was 7 % of the entire amount of dry matter and 10 % of the amount of cement. The composition of each granule thus formed corresponded to this average composition.

Claims

Claims:

1. A grain composition for the manufacture of a concrete or mortar mass, characterised in that it consists of granules, which each contain filler particles, to the surface of which the particles of a hydraulic binder are attached.

2. The composition according to Claim I₅ characterised in that its granules contain calcium carbonate particles, preferably in an amount of 50-70% of the weight of the granule, most preferably about 15%.

3. The composition according to Claim 1 or 2, characterised in that calcium carbonate particles, to the surface of which a plasticizer has been attached, have in turn been attached to the surface of the filler particles, whereby the particles of the hydraulic binder are attached to the filler particles through the calcium carbonate - plasticizer particles.

4. The composition according to any of the preceding claims, characterised in that the granules contain a pozzolanic binder, which preferably is a mixture containing kaolinite- containing calcined clay or kaolin, more preferably metakaolin sinter (MKS), which contains metakaolin, preferably 20-70 % by weight, kaolin, preferably 80-30 % by weight, and calcium oxide (CaO), preferably 5-20 % by weight.

5. The grain composition according to any of the preceding claims, characterised in that the granules have diameters of 10-100 μm, preferably 20-40 μm and they are spherical.

6. The grain composition according to any of the preceding claims, characterised in that the granules contain:

- a hydraulic binder, such as Portland cement (OPC);

- a filler, which preferably is limestone or SiO₂ stone;

- optionally, pozzolanic particles, such as a binder or a filler, which preferably is metakaolin sinter (MKS);

- calcium carbonate as nano-size particles (CaCO₃nano); and

- a plasticizer, which typically is a polymer of acrylic acid; and to the granules, the following can be added: - water, which preferably is industrial water or treated water containing Ca(HCO₃)₂.

7. The composition according to any of the preceding claims, characterised in that the pozzolanic filler particle is kaolinite-containing calcined clay or one of its forms, which is called kaolin, and that the pozzolanically reactive portion is metakaolin, of which there is 10-80 % present in this binder.

8. The composition according to any of the preceding claims, characterised in that the projection areas of the hydraulic binder particles are as large as or smaller than the surface areas of the filler particles of the granules.

9. A method for manufacturing the grain composition according to any of Claims 1-8, characterised by first attaching a plasticizer to the surface of the calcium carbonate particles, after which the formed calcium carbonate - plasticizer particles are attached to the surface of the filler particles, and finally attaching the particles of the hydraulic binder to the filler particles through the calcium carbonate - plasticizer particles.

10. The method according to Claim 9, characterised by adding a pozzolanic binder, for example in the form of filler particles, to the composition, which binder preferably has been rendered into the desired form by agglomerating and calcining.

11. The method according to Claim 10, characterised by carrying out the agglomeration and calcination by mixing the pozzolanic binder into water to reach a dry matter content of 30-70%, by drying the formed agglomerate slurry in a gas flow and by further calcining the agglomerates in the gas flow at 500-1100°C.

12. The method according to Claim 9 or 10, characterised by coating the hydraulic binder particles, before attaching them to the filler particles, with calcium carbonate particles, after which these calcium carbonate particles are coated with the plasticizer.

13. The method according to Claim 9 or 10, characterised by coating the hydraulic binder particles, before attaching them to the filler particles, with calcium carbonate particles, which in turn have been coated with the plasticizer.

14. A concrete or mortar mass, characterised in that it contains the grain composition according to any of claims 1-8 as well as fine aggregate and coarse aggregate.

15. The mass according to Claim 14, characterised in that the fine aggregate is limestone, preferably form-crushed limestone, or SiO₂ stone, preferably crushed aggregate or natural stone, and the coarse aggregate is crushed SiO₂ aggregate, SiO₂ natural stone, crushed limestone aggregate or so-called gangue from limestone mining.

16. A method for manufacturing a concrete or mortar mass, characterised by adding fine aggregate and coarse aggregate into the grain composition manufactured according to any of claims 9—13.

17. The method according to Claim 16, characterised by adding a pozzolanic binder or water or both into the mass.

18. Equipment for the manufacture of the grain composition according to any of claims 1- 8, characterised in that it contains

- a first container ( 1 ) ; - a cyclone separator (2), which is placed downstream of the first container (1);

- a pressure roller (3), which is attached to the bottom part of the cyclone separator (2);

- an opposed cylinder rotor distributor (4), which correspondingly is attached to the pressure roller (3); - coating equipment (6), which is in connection with the upper part of the cyclone separator (2) and to which a second container (5) is connected;

- mixing equipment (7), which is placed downstream of the coating equipment (6); and

- a storage tank (8), which is placed downstream of the mixing equipment (7).

19. The equipment according to Claim 18, characterised in that it contains calcination equipment, including a calcination furnace, which is in connection with the coating equipment (6) and the mixing equipment (7), in which calcinations equipment the pozzolanic binder can be rendered a desired form before it is brought in contact with the other components of the granule.