Composition: reaction powder concrete. Dry reaction powder concrete mixtures (RPC)

DRY REACTIVE POWDER CONCRETE MIXTURES –

NEW TYPES OF BINDERS FOR CREATION

DIFFERENT TYPES OF CONCRETE

Penza State University of Architecture and Construction. Russia

Reaction powder concretes (RPC) of the new generation are specific concretes of the future that do not contain coarse-grained and lump aggregates. This distinguishes them from fine-grained (sand) and crushed stone concrete. The grain composition of the fine-grained sand fraction is very narrow and ranges from 0.1-0.6 mm. The specific surface of such sand (P) does not exceed 400 cm2/g. The average specific surface area of the finely dispersed fraction, consisting of Portland cement (C), stone flour (CM) and microsilica (MS), which is the rheological matrix of the RPB, is within cm2/g. High dispersity is the basis for the adsorption processes of superplasticizers (SP) and a radical reduction in viscosity and yield strength with a minimum of water. Concrete mixtures for such concretes self-flow with a water content of 10-11% by weight of dry components. In cramped conditions, contact interactions between the particles of the components occur through the thinnest layers of water. In thin layers of water, reactions of hydration, hydrolysis of cement minerals and the interaction of hydrolyzed lime (portlandite) with microsilica and the finest particles of silica-containing rocks proceed intensively.

Due to the fact that in powder concrete the volumetric concentration of cement is 22-25%, the cement particles, in accordance with the previously proposed formula, do not contact each other, but are separated by nano-sized particles of microsilica, micrometric particles of ground sand and fine-grained sand. Under such conditions, in contrast to conventional sandy and crushed stone concrete, the topochemical hardening mechanism is inferior to the through-solution, ion-diffusion hardening mechanism. This has been convincingly confirmed by us in simple but original experiments to control the hardening of composite systems consisting of small quantities of coarse clinkers and granulated slags and a significant amount of highly dispersed marble with 10-12% water. In powdered concrete, the cement particles are separated by microsilica and stone flour particles. Thanks to the thinnest layers of water on the surfaces of the particles, the hardening processes of powder concrete proceed very quickly. Their daily strength reaches 40-60 MPa.

Let us estimate the average thickness of water cuffs on dispersed particles of reaction powder concrete and compare it with cuffs on cement particles. Let us take the average specific surface area of cement to be 3000 cm2/g, for stone flour to be 3800 cm2/g, and for microsilica to be 3000 cm2/g. Composition of the dispersed part of the RPB: C – 700 kg; KM – 350 kg; MK – 110 kg. Then the calculated specific surface area of the dispersed part of powder concrete will be 5800 cm2/g. Reactive powder concrete mixtures with hyperplasticizers (HP) they acquire gravitational spreadability at W/T = 0.1. The cement suspension with GP spreads under the influence of its own weight at W/C = 0.24.

Then, the average thickness of the water layer distributed on the surface of the particles is:

Thus, self-flowing of the cement suspension is ensured with an almost fivefold increase in the water layer compared to the RPB mixture. The high fluidity of reaction-powder concrete mixtures is due to strictly selected granulometry of rheologically active fine components in suspensions with a superplasticizer. The content of fine-grained sand, fraction 0.14-0.63 mm (average size 0.38 mm), should be such that the distance between its particles is within 55-65 microns. According to foreign researchers De Larrard and F. Sedran, the thickness of the rheological layer (for sands with d = 0.125-0.40) varies from 48 to 88 microns. With such layers, the yield strength we determined is 5-8 Pa.

The dispersed part of reaction-powder concrete, consisting of Portland cement, stone flour and MC, which is responsible for high gravitational fluidity, has an extremely high water requirement without the addition of SP. With a composition with a PC:CM:MC ratio of 1:0.5:0.1, gravity flow is realized at a water-solid ratio of 0.72-0.76, depending on the type of MC. Of the three studied microsilica – Chelyabinsk, Novokuznetsk and Bratsk – the latter has the highest water requirement. Its suspension with water begins to spread when the water content is 110% by weight of MK. Therefore, the presence of only 10% of the Bratsk MK increases the water requirement of the mixture of cement and ground sand from 34 to 76%. The introduction of superplasticizer Melflux 1641 F reduces the water content of the dispersed system C+KM+MK from 76 to 20% while maintaining fluidity. Thus, the water-reducing effect is 3.8 and reaches an almost fourfold reduction in water consumption. It should be noted that none of the studied microsilica is dispersed in water, and their suspensions are not diluted by any oligomeric superplasticizers of the first generation (C-3, Melment, Wiskoment, etc.), nor by polymeric hyperplasticizers of the second and third generation (Sika Viso Crete , Melflux 1641 F, Melflux 2641 F). Only in the presence of cement does MC become a realistically active component. The mechanism of this transformation, associated with the recharging of negatively charged surfaces of mineral particles with the calcium cation of hydrolytic lime, was identified by us in 1980. It is the presence of PC in the presence of SP that transforms a water-cement-sand suspension with MC into a low-viscosity and aggregation-stable system.

Dry reaction powder concrete mixtures (DRPC), intended for the production of crushed stone-free self-compacting concrete for monolithic and prefabricated construction, can become a new, main type of composite binder for the production of many types of concrete (figure). The high fluidity of reaction-powder concrete mixtures makes it possible to additionally fill them with crushed stone while maintaining fluidity and use them for self-compacting high-strength concrete; when filled with sand and crushed stone - for vibration technologies of molding, vibrocompression and calendering. At the same time, concrete produced using vibration and vibro-force compaction technologies can have higher strength than cast concrete. At a higher degree, concrete for general construction purposes of classes B20-B40 is obtained.

Rice. 1 Main areas of application of dry

reaction-powder concrete mixtures

It is safe to say that in the future, cement binder will be replaced by dry reaction powder binder (DRP) based on the following positive factors:

1. Extremely high strength RPV, reaching 120-160 MPa, significantly exceeding the strength of superplasticized Portland cement due to the transformation of “ballast” lime into cementing hydrosilicates.

2. Multifunctionality of physical and technical properties of concrete with the introduction of short dispersed steel fibers into it: low water absorption (less than 1%), high frost resistance (more than 1000 cycles), high axial tensile strength (10-15 MPa) and bending tensile strength ( 40-50 MPa), high impact strength, high resistance to carbonate and sulfate corrosion, etc.;

3. High technical and economic indicators of SRPB production at cement factories that have a complex of equipment: drying, grinding, homogenization, etc.;

4. Widespread occurrence of quartz sand in many regions of the globe, as well as stone flour from the technology of enrichment of ferrous and non-ferrous metals using magnetic separation and flotation methods;

5. Huge reserves of stone crushing screenings with their complex processing into fine-grained crushed stone and stone flour;

6. Possibility of using technology for joint grinding of reaction filler, cement and superplasticizer;

7. Possibility of using SRPB for the production of high-strength, extra-high-strength crushed stone and sandy concrete of a new generation, as well as concrete for general construction purposes by varying the ratio of aggregate and binder;

8. Possibility of producing high-strength lightweight concrete using non-water-absorbing microglass and microsolospheres with the implementation of high strength reaction-powder binder;

9. Possibility of producing high-strength glue and bonds for repair work.

The staff of the department “Technology of concrete, ceramics and binders” is not able to develop on its own all the areas indicated in the figure due to the lack of necessary conditions, lack of modern equipment and instruments, financing of the most important works, including promising ones. Judging by the publications in Russia, there is practically no development of particularly high-strength reaction-powder concrete of classes B 120, B 140. A large number of publications are devoted to the improvement of concrete for general construction purposes in order to save cement by 10-20% while maintaining the same strength.

Over the past five years, publications have appeared devoted to the development of concrete classes B 60-B 100 using organo-mineral additives without the use of significant quantities of rheologically and reactive stone flour (dispersed fillers) to increase the volume of the rheological matrix and to enhance the effect of superplasticizers and hyperplasticizers new generation. And without it, it is impossible to produce self-compacting concrete mixtures with a spread of a standard cone of 70-80 cm. As for the use of nanotechnology, it is not able to radically change the imperfect, extremely defective structure of concrete of classes B30-B40. Therefore, it is unlikely that it will be possible to achieve high strength equal to 150-200 MPa through nanotechnology in the next 10-15 years. It is necessary to use what lies on the “surface”, what has been achieved by three revolutionary stages in the chemistry and mechanics of concrete on the evolutionary path of development of its technology. Nanotechnology will be necessary to improve the low-defect structure of high-strength concrete with an increase in strength above 200-250 MPa.

The future of concrete is connected with the use of stone flour, because only the high fluidity of a mixed cement-dispersed matrix, which has a 2-3-fold water-reducing effect, makes it possible to achieve (with an optimal concrete structure) “high” rheology, and through it high density and strength of concrete . It is through the rational rheology of concrete mixtures that it is necessary to follow into the future of concrete, through the creation of rheological matrices of the first and second kind, through a radical change in the recipe and structure of the plasticized concrete mixture. The basic principles of creating such concretes and calculating their composition are fundamentally different from traditional densely packed concretes and self-compacting plasticized concretes with organo-mineral additives.

Literature

1. , Kalashnikov high-strength concretes of a new generation // Popular concrete science. St. Petersburg, No. 2 (16), 2007. pp. 44-49.

2. Kalashnikov rheological matrices and powder concretes of a new generation. Collection of articles of the International Scientific and Practical Conference “Composite building materials. Theory and practice". Penza. Privolzhsky House of Knowledge, 2007. pp. 9-18.

3. To the theory of hardening of composite cement binders. Materials of the International Scientific and Technical Conference “Current Issues of Construction”. Saransk, Moscow State University, 2004. pp. 119-124.

4. De Larrard, F. Sedran. Optimization of ultrahight-performance concrete by the use of a packing model. Cem Concrete Res. – Vol., 1994. – S. .

5 Kalashnikov rational rheology into the future of concrete. Part 1. Types of rheological matrices in a concrete mixture, a strategy for increasing the strength of concrete and saving it in structures // Concrete Technology, No. 5, 2007. P.8-10.

6 Kalashnikov rational rheology into the future of concrete. Part 2. Finely dispersed rheological matrices and powder concretes of the new generation // Concrete Technology, No. 6, 2007. P. 8-11.

7 Kalashnikov rational rheology into the future of concrete. Part 3. From high-strength and extra-high-strength concretes of the future to superplasticized concretes general purpose of the present // Concrete Technologies, No. 1, 2008. P.22-26

8 Kalashnikov principles of creating high-strength and extra-high-strength concrete // Popular concrete science. Saint Petersburg. No. 3, 2008. P.20-22.

9 Kalashnikov compositions of high-strength self-compacting concrete // Construction materials, No. 10, 2008. P.4-6.

01.06.2008 16:51:57

The article describes the properties and capabilities of high-strength powder concrete, as well as the areas and technologies of their application.

High rates of construction of residential and industrial buildings with new and unique architectural forms and especially special, highly loaded structures (such as long-span bridges, skyscrapers, offshore oil platforms, tanks for storing gases and liquids under pressure, etc.) required the development of new effective concretes. Significant progress in this has been especially noted since the late 80s of the last century. Modern high-quality concretes (VKB) classification combine a wide range of concretes for various purposes: high-strength and ultra-high-strength concretes [see. Bornemann R., Fenling E. Ultrahochfester Beton-Entwicklung und Verhalten.// Leipziger Massivbauseminar, 2000, Bd. 10; Schmidt M. Bornemann R. M?glichkeiten und Crensen von Hochfestem Beton.// Proc. 14, Jbausil, 2000, Bd. 1], self-compacting concrete, highly corrosion-resistant concrete. These types of concrete meet high requirements for compressive and tensile strength, crack resistance, impact strength, wear resistance, corrosion resistance, and frost resistance.

Of course, the transition to new types of concrete was facilitated, firstly, by revolutionary achievements in the field of plasticization of concrete and mortar mixtures, and secondly, by the emergence of the most active pozzolanic additives - microsilica, dehydrated kaolins and highly dispersed ashes. Combinations of superplasticizers and especially environmentally friendly hyperplasticizers on a polycarboxylate, polyacrylate and polyglycolic base make it possible to obtain superfluid cement-mineral dispersed systems and concrete mixtures. Thanks to these achievements, the number of components in concrete with chemical additives reached 6–8, the water-cement ratio decreased to 0.24–0.28 while maintaining plasticity, characterized by a cone settlement of 4–10 cm. In self-compacting concrete (Selbstverdichtender Beton-SVB) with the addition of stone flour (CM) or without it, but with the addition of MC in highly workable concretes (Ultrahochfester Beton, Ultra hochleistung Beton) on hyperplasticizers, in contrast to those cast on traditional SPs, the perfect fluidity of concrete mixtures is combined with low sedimentation and self-compaction with spontaneous removal of air.

“High” rheology with significant water reduction in superplasticized concrete mixtures is ensured by a fluid rheological matrix, which has different scale levels of the structural elements that make it up. In crushed stone concrete, the rheological matrix at various micro-meso levels is a cement-sand mortar. In plasticized concrete mixtures for high-strength concrete for crushed stone as a macrostructural element, the rheological matrix, the proportion of which should be significantly higher than in conventional concrete, is a more complex dispersion consisting of sand, cement, stone flour, microsilica and water. In turn, for sand in conventional concrete mixtures, the rheological matrix at the micro level is a cement-water paste, the proportion of which can be increased to ensure fluidity by increasing the amount of cement. But this, on the one hand, is uneconomical (especially for concrete classes B10 - B30); on the other hand, paradoxically, superplasticizers are poor water-reducing additives for Portland cement, although they were all created and are being created for it. Almost all superplasticizers, as we have shown since 1979, “work” much better on many mineral powders or on their mixture with cement [see. Kalashnikov V.I. Fundamentals of plasticization of mineral dispersed systems for the production of building materials: A dissertation in the form of a scientific report for the degree of Doctor of Science. tech. Sci. – Voronezh, 1996] than with pure cement. Cement is a water-unstable, hydrating system that forms colloidal particles immediately after contact with water and quickly thickens. And colloidal particles in water are difficult to disperse with superplasticizers. An example is clay suspensions that are poorly susceptible to super-liquefaction.

Thus, the conclusion suggests itself: stone flour must be added to cement, and it will increase not only the rheological effect of SP on the mixture, but also the share of the rheological matrix itself. As a result, it becomes possible to significantly reduce the amount of water, increase the density and increase the strength of concrete. Adding stone flour will practically be equivalent to increasing cement (if the water-reducing effects are significantly higher than when adding cement).

It is important here to focus attention not on replacing part of the cement with stone flour, but adding it (and a significant proportion - 40–60%) to Portland cement. Based on the polystructural theory in 1985–2000. All work on changing the polystructure had the goal of replacing 30–50% of Portland cement with mineral fillers to save it in concrete [see. Solomatov V.I., Vyrovoy V.N. et al. Composite building materials and structures with reduced material consumption. – Kyiv: Budivelnik, 1991; Aganin S.P. Concretes of low water demand with modified quartz filler: Abstract for the academic competition. Ph.D. degrees tech. Sci. – M, 1996; Fadel I. M. Intensive separate technology of concrete filled with basalt: Abstract of thesis. Ph.D. tech. Sciences - M, 1993]. The strategy of saving Portland cement in concrete of the same strength will give way to the strategy of saving concrete with 2–3 times higher strength not only in compression, but also in flexural and axial tension, and upon impact. Saving concrete in more openwork structures will give a higher economic effect than saving cement.

Considering the compositions of rheological matrices at various scale levels, we establish that for sand in high-strength concrete, the rheological matrix at the micro level is a complex mixture of cement, flour, silica, superplasticizer and water. In turn, for high-strength concrete with microsilica, for a mixture of cement and stone flour (equal dispersion) as structural elements, another rheological matrix appears with a smaller scale level - a mixture of microsilica, water and superplasticizer.

For crushed stone concrete, these scales of structural elements of rheological matrices correspond to the scale of the optimal granulometry of the dry components of concrete to obtain its high density.

Thus, the addition of stone flour performs both a structural-rheological function and a matrix-filling function. For high-strength concrete, the reaction-chemical function of stone flour is no less important, which is performed with a higher effect by reactive microsilica and microdehydrated kaolin.

The maximum rheological and water-reducing effects caused by the adsorption of SP on the surface of the solid phase are genetically characteristic of finely dispersed systems with a high interface surface.

Table 1.

Rheological and water-reducing effect of SP in water-mineral systems

Type of dispersed powder and plasticizer	SP dosage,%
CaCO3 (Mg 150)
BaCO3 (Melment)

Ca(OH)2 (LST)

Cement PO "Volskcement" (S-3)
Opoka of the Penza field (S-3)
Ground glass TF10 (S-3)

From Table 1 it can be seen that in Portland cement casting suspensions with SP, the water-reducing effect of the latter is 1.5–7.0 times (sic!) higher than in mineral powders. For rocks this excess can reach 2–3 times.

Thus, the combination of hyperplasticizers with microsilica, stone flour or ash made it possible to increase the level of compressive strength to 130–150, and in some cases to 180–200 MPa or more. However, a significant increase in strength leads to an intensive increase in fragility and a decrease in Poisson's ratio to 0.14–0.17, which leads to the risk of sudden destruction of structures in emergency situations. Getting rid of this negative property of concrete is carried out not only by reinforcing the latter with rod reinforcement, but by combining rod reinforcement with the introduction of fibers from polymers, glass and steel.

The basics of plasticization and water reduction of mineral and cement dispersed systems were formulated in the doctoral dissertation of V.I. Kalashnikov. [cm. Kalashnikov V.I. Fundamentals of plasticization of mineral dispersed systems for the production of building materials: A dissertation in the form of a scientific report for the degree of Doctor of Science. tech. Sci. – Voronezh, 1996] in 1996 based on previously completed work in the period from 1979 to 1996. [Kalashnikov V.I., Ivanov I.A. On the structural and rheological state of extremely liquefied highly concentrated disperse systems. // Proceedings of the IV National Conference on Mechanics and Technology of Composite Materials. – Sofia: BAN, 1985; Ivanov I. A., Kalashnikov V. I. Efficiency of plasticization of mineral dispersed compositions depending on the concentration of the solid phase in them. // Rheology of concrete mixtures and its technological tasks. Abstract. Report of the III All-Union Symposium. - Riga. – FIR, 1979; Kalashnikov V.I., Ivanov I.A. On the nature of plasticization of mineral dispersed compositions depending on the concentration of the solid phase in them. // Mechanics and technology of composite materials. Materials of the II National Conference. – Sofia: BAN, 1979; Kalashnikov V.I. On the reaction of various mineral compositions to naphthalene-sulfonic acid superplasticizers and the influence of instant alkalis on it. // Mechanics and technology of composite materials. Materials of the III National Conference with the participation of foreign representatives. – Sofia: BAN, 1982; Kalashnikov V.I. Accounting for rheological changes in concrete mixtures with superplasticizers. // Materials of the IX All-Union Conference on Concrete and Reinforced Concrete (Tashkent, 1983). - Penza. – 1983; Kalashnikov V.I., Ivanov I.A. Features of rheological changes in cement compositions under the influence of ion-stabilizing plasticizers. // Collection of works “Technological mechanics of concrete”. – Riga: RPI, 1984]. These are the prospects for the targeted use of the highest water-reducing activity of SP in finely dispersed systems, the features of quantitative rheological and structural-mechanical changes in superplasticized systems, which consist in their avalanche-like transition from solid-phase to liquid states with super-low addition of water. These are developed criteria for gravitational spreading and post-thixotropic flow resource of highly dispersed plasticized systems (under the influence of their own weight) and spontaneous leveling of the day surface. This is an advanced concept of the extreme concentration of cement systems with fine powders from rocks of sedimentary, igneous and metamorphic origin, selective for levels of high water reduction to SP. Most important results, obtained in these works, consist in the possibility of a 5–15-fold reduction in water consumption in dispersions while maintaining gravitational spreadability. It has been shown that by combining rheologically active powders with cement it is possible to enhance the effect of SP and obtain high-density castings. It is these principles that are implemented in reaction-powder concrete with an increase in their density and strength (Reaktionspulver concrete - RPB or Reactive Powder Concrete - RPC [see Dolgopolov N.N., Sukhanov M.A., Efimov S.N. New type of cement: structure of cement stone. // Construction materials. – 1994. – No. 115]). Another result is an increase in the reducing effect of SP with increasing dispersion of powders [see. Kalashnikov V.I. Fundamentals of plasticization of mineral dispersed systems for the production of building materials: A dissertation in the form of a scientific report for the degree of Doctor of Science. tech. Sci. – Voronezh, 1996]. It is also used in powdered fine concrete by increasing the proportion of fine constituents by adding silica fume to the cement. What is new in the theory and practice of powder concrete is the use of fine sand of a fraction of 0.1–0.5 mm, which made the concrete fine-grained in contrast to ordinary sand on sand of a fraction of 0–5 mm. We calculated the average specific surface of the dispersed part of powder concrete (composition: cement - 700 kg; fine sand 0.125–0.63 mm - 950 kg, basalt flour Ssp = 380 m2/kg - 350 kg, microsilica Svd = 3200 m2/ kg - 140 kg) with its content of 49% of the total mixture with fine-grained sand fraction 0.125–0.5 mm shows that with the fineness of MK Smk = 3000 m2/kg, the average surface of the powder part is Svd = 1060 m2/kg, and with Smk = 2000 m2 /kg – Svd = 785 m2/kg. It is from these finely dispersed components that fine-grained reaction-powder concretes are made, in which the volumetric concentration of the solid phase without sand reaches 58–64%, and with sand – 76–77% and is slightly inferior to the concentration of the solid phase in superplasticized heavy concrete (Cv = 0, 80–0.85). However, in crushed stone concrete the volumetric concentration of the solid phase minus crushed stone and sand is much lower, which determines the high density of the dispersed matrix.

High strength is ensured by the presence not only of microsilica or dehydrated kaolin, but also of reactive powder from ground rock. According to the literature, fly ash, baltic, limestone or quartz flour are mainly introduced. Wide opportunities in the production of reactive powder concrete opened up in the USSR and Russia in connection with the development and research of composite binders of low water demand by Yu. M. Bazhenov, Sh. T. Babaev, A. Komarov. A., Batrakov V.G., Dolgopolov N.N. It has been proven that replacing cement in the process of grinding VNV with carbonate, granite, quartz flour up to 50% significantly increases the water-reducing effect. The W/T ratio, which ensures the gravitational spreadability of crushed stone concrete, is reduced to 13–15% in comparison with the usual introduction of SP; the strength of concrete on such VNV-50 reaches 90–100 MPa. Essentially, modern powder concrete can be obtained based on VNV, microsilica, fine sand and dispersed reinforcement.

Dispersed-reinforced powder concrete is very effective not only for load-bearing structures with combined reinforcement with prestressed reinforcement, but also for the production of very thin-walled, including spatial, architectural parts.

According to the latest data, textile reinforcement of structures is possible. It was the development of textile-fiber production of (fabric) volumetric frames from high-strength polymer and alkali-resistant threads in developed foreign countries that motivated the development, more than 10 years ago in France and Canada, of reaction-powder concrete with SP without large aggregates with especially fine quartz aggregate, filled with stone powders and microsilica. Concrete mixtures made from such fine-grained mixtures spread under the influence of their own weight, completely filling the dense mesh structure of the woven frame and all filigree-shaped joints.

“High” rheology of powdered concrete mixtures (PBC) provides a yield strength of 0 = 5–15 Pa at a water content of 10–12% of the mass of dry components, i.e. only 5–10 times higher than in oil paints. With this?0, to determine it, you can use the mini-hydrometric method, developed by us in 1995. The low yield strength is ensured optimal thickness layers of rheological matrix. From a consideration of the topological structure of the PBS, the average thickness of the layer X is determined by the formula:

where is the average diameter of sand particles; – volume concentration.

For the composition given below at W/T = 0.103, the thickness of the interlayer will be 0.056 mm. De Larrard and Sedran found that for finer sands (d = 0.125–0.4 mm) the thickness varies from 48 to 88 μm.

Increasing the particle interlayer reduces viscosity and ultimate shear stress and increases fluidity. Fluidity can increase by adding water and introducing SP. IN general view the influence of water and SP on the change in viscosity, ultimate voltage shear and yield are ambiguous (Fig. 1).

The superplasticizer reduces the viscosity to a much lesser extent than the addition of water, while the decrease in the yield strength due to SP is much higher than under the influence of water.

Rice. 1. Effect of SP and water on viscosity, yield stress and fluidity

The main properties of superplasticized extremely filled systems are that the viscosity can be quite high and the system can flow slowly if the yield stress is low. For conventional systems without SP, the viscosity may be low, but the increased yield strength prevents them from spreading, since they do not have a post-thixotropic flow resource [see. Kalashnikov V.I., Ivanov I.A. Features of rheological changes in cement compositions under the influence of ion-stabilizing plasticizers. // Collection of works “Technological mechanics of concrete”. – Riga: RPI, 1984].

Rheological properties depend on the type and dosage of SP. The influence of three types of SP is shown in Fig. 2. The most effective joint venture is Woerment 794.

Rice. 2 Influence of the type and dosage of SP on?o: 1 – Woerment 794; 2 – S-3; 3 – Melment F 10

At the same time, it was not the domestic SP S-3 that turned out to be less selective, but the foreign SP based on melamine Melment F10.

The spreadability of powdered concrete mixtures is extremely important when forming concrete products with woven volumetric mesh frames laid in a mold.

Such volumetric openwork-fabric frames in the form of a T-beam, I-beam, channel and other configurations allow for quick reinforcement, which consists of installing and fixing the frame in a mold, followed by pouring suspension concrete, which easily penetrates through frame cells measuring 2–5 mm (Fig. 3) . Fabric frames can radically increase the crack resistance of concrete when exposed to alternating temperature fluctuations and significantly reduce deformations.

The concrete mixture should not only flow easily locally through the mesh frame, but also spread when filling the form by “reverse” penetration through the frame as the volume of the mixture in the form increases. To assess the flowability, powder mixtures of the same composition in terms of the content of dry components were used, and the spreadability from the cone (for the shaking table) was regulated by the amount of SP and (partially) water. The spreading was blocked by a mesh ring with a diameter of 175 mm.

Rice. 3 Sample fabric frame

Rice. 4 Mixture spreads with free and blocked spreading

The mesh had a clear size of 2.8×2.8 mm with a wire diameter of 0.3×0.3 mm (Fig. 4). Control mixtures were made with spreads of 25.0; 26.5; 28.2 and 29.8 cm. As a result of experiments, it was found that with increasing fluidity of the mixture, the ratio of the diameters of free dc and blocked spread d decreases. In Fig. Figure 5 shows the change in dc/dbotdc.

Rice. 5 Change dc/db from the free spread value dc

As follows from the figure, the difference in the spread of the mixture dc and db disappears with fluidity, characterized by a free spread of 29.8 cm. At dc. = 28.2, the spread through the mesh decreases by 5%. The mixture with a spread of 25 cm experiences especially great braking when spreading through the mesh.

In this regard, when using mesh frames with a cell of 3–3 mm, it is necessary to use mixtures with a spread of at least 28–30 cm.

The physical and technical properties of dispersed-reinforced powder concrete, reinforced with 1% by volume steel fibers with a diameter of 0.15 mm and a length of 6 mm, are presented in Table 2

Table 2.

Physical and technical properties of powder concrete with low water demand binder using domestic SP S-3

Name of properties	Unit	Indicators
Density
Porosity
Compressive Strength
Bending tensile strength
Axial tensile strength
Elastic modulus
Poisson's ratio

Water absorption
Frost resistance	number of cycles

According to foreign data, with 3% reinforcement, compressive strength reaches 180–200 MPa, and axial tensile strength – 8–10 MPa. Impact strength increases more than tenfold.

The possibilities of powder concrete are far from exhausted, given the effectiveness of hydrothermal treatment and its influence on increasing the proportion of tobermorite, and, accordingly, xonotlite

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Owners of patent RU 2531981:

There is a known method for the manufacture of decorative building products and/or decorative coatings by mixing with water a binder containing Portland cement clinker, a modifier including an organic water-reducing component and a certain amount of hardening accelerator and gypsum, pigments, fillers, mineral and chemical (functional) additives, and the resulting mixture kept until the bentonite clay (functional additive, mixture stabilizer) is saturated with propylene glycol (an organic water-reducing component), the resulting complex is fixed with the gelling agent hydroxypropylcellulose, laid, molded, compacted and heat treated. Moreover, mixing the dry components and preparing the mixture is carried out in different mixers (see RF patent No. 2084416, MPK6 C04B 7/52, 1997).

The disadvantage of this solution is the need to use various equipment for mixing the components of the mixture and subsequent compaction operations, which complicates and increases the cost of the technology. In addition, when using this method it is impossible to obtain products with thin and openwork elements.

There is a known method for preparing a mixture for the production of construction products, which includes activating the binder by co-grinding Portland cement clinker with a dry superplasticizer and subsequent mixing with filler and water, whereby the activated filler is first mixed with 5-10% mixing water, then the activated binder is introduced and the mixture is mixed, after which 40 - 60% of mixing water is introduced and the mixture is stirred, then the remaining water is introduced and final mixing is carried out until a homogeneous mixture is obtained. Step-by-step mixing of the components is carried out within 0.5-1 minutes. Products made from the resulting mixture must be kept at a temperature of 20°C and a humidity of 100% for 14 days (see RF patent No. 2012551, MPK5 C04B 40/00, 1994).

The disadvantage of this known method is the complex and expensive operation of joint grinding of the binder and superplasticizer, which requires large expenses for the organization of the mixing and grinding complex. In addition, when using this method it is impossible to obtain products with thin and openwork elements.

A known composition for the preparation of self-compacting concrete contains:

100 wt. parts of cement,

50-200 wt. parts of sand mixtures from calcined bauxite of different granulometric composition, the finest sand of average granulometric composition less than 1 mm, the coarsest sand of average granulometric composition less than 10 mm;

5-25 wt. parts of ultra-small particles of calcium carbonate and white soot, and the white soot content is no more than 15 wt. parts;

0.1-10 wt. antifoam parts;

0.1-10 wt. parts of superplasticizer;

15-24 wt. fiber parts;

10-30 wt. parts of water.

The mass ratio between the amount of ultra-small particles of calcium carbonate in concrete and the amount of white soot can reach 1:99-99:1, preferably 50:50-99:1 (see RF patent No. 2359936, IPC S04B 28/04 S04B 111/20 S04B 111/62 (2006.01), 2009, paragraph 12).

The disadvantage of this concrete is the use of expensive sands from calcined bauxite, usually used in aluminum production, as well as an excessive amount of cement, which leads, accordingly, to an increase in the consumption of other very expensive components of concrete and, accordingly, to an increase in its cost.

The search showed that no solutions were found that would ensure the production of reaction-powder self-compacting concrete.

There is a known method for preparing concrete with the addition of fibers, in which all components of concrete are mixed to obtain concrete with the required fluidity, or dry components such as cement, various types of sand, ultra-fine particles of calcium carbonate, white soot and, possibly, a superplasticizer and an antifoam agent are first mixed, after which water is added to the mixture, and, if necessary, a superplasticizer, and an anti-foaming agent, if present in liquid form, and, if necessary, fibers, and mixed until concrete with the required fluidity is obtained. After mixing, for example, for 4-16 minutes, the resulting concrete can be easily molded due to its very high fluidity (see RF patent No. 2359936, IPC S04B 28/04, S04B 111/20, S04B 111/62 (2006.01), 2009 ., paragraph 12). This solution was adopted as a prototype.

The resulting self-compacting concrete with ultra-high properties can be used for the manufacture of prefabricated elements such as pillars, cross beams, beams, floors, tiles, artistic structures, prestressed elements or composite materials, material for sealing gaps between structural elements, elements of sewage systems or in architecture.

The disadvantage of this method is the high consumption of cement to prepare 1 m 3 of the mixture, which entails an increase in the cost of the concrete mixture and products made from it due to the increased consumption of other components. In addition, the method of using the resulting concrete described in the invention does not provide any information on how, for example, artistic openwork and thin-walled concrete products can be produced.

There are widely known methods for manufacturing various concrete products, when concrete poured into a mold is subsequently subjected to vibration compaction.

However, using such known methods it is impossible to obtain artistic, openwork and thin-walled concrete products.

There is a known method for producing concrete products in packaging forms, which consists of preparing a concrete mixture, feeding the mixture into molds, and hardening. An air- and moisture-proofing form is used in the form of thin-walled multi-chamber packaging forms, covered with an air- and moisture-proofing coating after feeding the mixture into them. Hardening of products is carried out in sealed chambers for 8-12 hours (see patent for invention of Ukraine No. UA 39086, MPK7 B28B 7/11; B28B 7/38; C04B 40/02, 2005).

The disadvantage of this known method is the high cost of the forms used for the manufacture of concrete products, as well as the impossibility of producing artistic, openwork and thin-walled concrete products in this way.

The first task is to obtain the composition of a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with the required workability and the necessary strength characteristics, which will reduce the cost of the resulting self-compacting concrete mixture.

The second task is to increase the strength characteristics at one day of age with optimal workability of the mixture and improve the decorative properties of the front surfaces of concrete products.

The first task is solved due to the fact that a method has been developed for preparing a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture, which consists in mixing the components of the concrete mixture until the required fluidity is obtained, in which the mixing of the components of the fiber-reinforced concrete mixture is carried out sequentially, and initially water and a hyperplasticizer are mixed in the mixer, then add cement, microsilica, stone flour and mix the mixture for 2-3 minutes, after which sand and fiber are added and mixed for 2-3 minutes until a fiber-reinforced concrete mixture is obtained containing the following components, wt.%:

The total time for preparing the concrete mixture is from 12 to 15 minutes.

The technical result from the use of the invention is to obtain a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high fluidity properties, improving the quality and spreadability of the fiber-reinforced concrete mixture, due to a specially selected composition, sequence of introduction and mixing time of the mixture, which leads to a significant increase in fluidity and strength characteristics concrete up to M1000 and higher, reducing the required thickness of products.

Mixing the ingredients in a certain sequence, when initially a measured amount of water and hyperplasticizer is mixed in the mixer, then cement, microsilica, stone flour are added and mixed for 2-3 minutes, after which sand and fiber are added and the resulting concrete mixture is mixed for 2-3 minutes. 3 minutes, allows for a significant increase in the quality and fluidity characteristics (workability) of the resulting self-compacting, extra-high-strength reaction-powder fiber-reinforced concrete mixture.

makes it possible to obtain a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, high strength characteristics and at the same time low cost.

The use of the above components, subject to the specified proportions in quantitative ratio, allows, when obtaining a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with the required fluidity and high strength properties, to ensure a low cost of the resulting mixture and thus increase its consumer properties. The use of components such as microsilica and stone flour makes it possible to reduce the percentage of cement, which entails a reduction in the percentage of other expensive components (hyperplasticizer, for example), and also to abandon the use of expensive sands made from calcined bauxite, which also leads to a reduction in the cost of concrete mixture, but does not affect its strength properties.

The second task is solved due to the fact that a method has been developed for the manufacture of products in molds from a fiber-reinforced concrete mixture prepared in the manner described above, which consists of feeding the mixture into the molds and subsequent holding for curing, and initially spraying on the inner, working surface of the mold thin layer water, and after filling the mold with the mixture, spray a thin layer of water on its surface and cover the mold with a technological tray.

Moreover, the mixture is fed into the molds sequentially, covering the filled mold on top with a technological pallet; after installing the technological pallet, the product manufacturing process is repeated many times, placing the next mold on the technological pallet above the previous one.

The technical result from the use of the invention is to improve the quality of the front surface of the product, significantly increase the strength characteristics of the product, through the use of a self-compacting fiber-reinforced concrete mixture with very high flow properties, special processing of forms and organization of care for concrete at one day of age. Organization of care for concrete at one day of age consists of ensuring sufficient waterproofing of forms with concrete poured into them by covering the top layer of concrete in the form with a water film and covering the forms with pallets.

The technical result is achieved through the use of a self-compacting fiber-reinforced concrete mixture with very high fluidity properties, which allows the production of very thin and openwork products of any configuration, repeating any textures and types of surfaces, eliminates the process of vibration compaction when molding products, and also allows the use of any shapes (elastic, fiberglass , metal, plastic, etc.) for the production of products.

Preliminary wetting of the form with a thin layer of water and the final operation of spraying a thin layer of water on the surface of the poured fiber-reinforced concrete mixture, covering the form with concrete with the next technological pallet in order to create a sealed chamber for better maturation of concrete allows you to eliminate the appearance of air pores from trapped air, achieve High Quality the front surface of products, reduce the evaporation of water from hardening concrete and increase the strength characteristics of the resulting products.

The number of molds poured simultaneously is selected based on the volume of the resulting self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture.

Obtaining a self-compacting fiber-reinforced concrete mixture with very high fluidity properties and, due to this, improved workability qualities, makes it possible not to use a vibrating table in the manufacture of artistic products and simplifies the manufacturing technology, while increasing the strength characteristics of artistic concrete products.

The technical result is achieved due to the specially selected composition of the fine-grained self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture, the sequence of components introduction, the method of processing forms and the organization of care of concrete at one day of age.

Advantages of this technology and the concrete used:

Use of sand size modulus fr. 0.125-0.63;

Absence of coarse aggregate in the concrete mixture;

Possibility of manufacturing concrete products with thin and openwork elements;

Ideal surface of concrete products;

Possibility of manufacturing products with a given surface roughness and texture;

High grade concrete compressive strength, not less than M1000;

High grade concrete bending strength, not less than Ptb100;

The present invention is explained in more detail below with the help of non-limiting examples.

Fig. 1 (a, b) - diagram of the manufacture of products - pouring the resulting fiber-reinforced concrete into molds;

Fig. 2 is a top view of the product obtained using the claimed invention.

A method for producing a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, containing the above components, is carried out as follows.

First, all components of the mixture are weighed. Then a measured amount of water and hyperplasticizer is poured into the mixer. After which the mixer is turned on. During the process of mixing water, the hyperplasticizer is sequentially poured following components mixtures: cement, microsilica, stone flour. If necessary, iron oxide pigments can be added to color concrete in bulk. After introducing these components into the mixer, the resulting suspension is stirred for 2 to 3 minutes.

At the next stage, sand and fiber are sequentially introduced and the concrete mixture is mixed for 2 to 3 minutes. After which the concrete mixture is ready for use.

During the preparation of the mixture, a strength gain accelerator is introduced.

The resulting self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties is a liquid consistency, one of the indicators of which is the spreading of the Hagerman cone on the glass. For the mixture to spread well, the spread must be at least 300 mm.

As a result of applying the claimed method, a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties is obtained, which contains the following components: Portland cement PC500D0, sand of fractions from 0.125 to 0.63, hyperplasticizer, fibers, microsilica, stone flour, set accelerator strength and water. When implementing the method for producing a fiber-reinforced concrete mixture, the following ratio of components is observed, wt.%:

Moreover, when implementing the method for producing a fiber-reinforced concrete mixture, stone flour is used from various natural materials or waste, such as, for example, quartz flour, dolomite flour, limestone flour, etc.

The following brands of hyperplasticizer can be used: Sika ViscoCrete, Glenium, etc.

When preparing the mixture, a strength development accelerator, for example Master X-Seed 100 (X-SEED 100) or similar strength development accelerators, may be added.

The resulting self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties can be used in the production of artistic products with a complex configuration, for example, openwork fences (see Fig. 2). Use the resulting mixture immediately after its preparation.

A method for manufacturing concrete products from a self-compacting, extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, obtained by the method described above and having the specified composition, is carried out as follows.

For the manufacture of openwork products by pouring a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, elastic (polyurethane, silicone, mold-plastic) or rigid plastic forms are used 1. Conventionally, a form with a simple configuration is shown, however, this type of form is not indicative and is chosen for simplifying the diagram. The mold is installed on the technological tray 2. A thin layer of water is sprayed onto the inner working surface 3 of the mold, this further reduces the number of trapped air bubbles on the front surface of the concrete product.

After this, the resulting fiber-reinforced concrete mixture 4 is poured into a mold, where it spreads and self-compacts under the influence of its own weight, squeezing out the air in it. After self-leveling of the concrete mixture in the mold, a thin layer of water is sprayed onto the concrete poured into the mold to ensure a more intense release of air from the concrete mixture. Then the form filled with fiber-reinforced concrete mixture is covered on top with the next technological tray 2, which creates a closed chamber for a more intensive set of concrete strength (see Fig. 1 (a)).

A new mold is placed on this pallet, and the product manufacturing process is repeated. Thus, from one portion of the prepared concrete mixture, several forms can be filled sequentially, installed one above the other, which increases the efficiency of using the prepared fiber-reinforced concrete mixture. Forms filled with fiber-reinforced concrete mixture are left to cure the mixture for approximately 15 hours.

After 15 hours, the concrete products are unmolded and sent for grinding of the back side, and then into a steaming chamber or into a heat-humidity treatment (HHT) chamber, where the products are kept until they reach full strength.

The use of the invention makes it possible to produce highly decorative openwork and thin-walled high-strength concrete products of grade M1000 and higher using simplified casting technology without the use of vibration compaction.

The invention can be carried out using the listed known components, subject to the quantitative proportions and described technological regimes. When implementing the invention, known equipment can be used.

An example of the implementation of a method for preparing a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties.

First, all components of the mixture are weighed and measured in the given quantities (wt.%):

Then a measured amount of water and Sika ViscoCrete 20 Gold hyperplasticizer is poured into the mixer. After which the mixer is turned on and the components are mixed. During the process of mixing water and hyperplasticizer, the following components of the mixture are sequentially poured in: Portland cement PC500 D0, microsilica, quartz flour. The mixing process is carried out continuously for 2-3 minutes.

At the next stage, sand fr. is sequentially introduced. 0.125-0.63 and steel fiber 0.22×13mm. The concrete mixture is mixed for 2-3 minutes.

Reducing the mixing time does not allow obtaining a homogeneous mixture, and increasing the mixing time does not provide additional improvement in the quality of the mixture, but delays the process.

After which the concrete mixture is ready for use.

The total production time for fiber-reinforced concrete mixture is from 12 to 15 minutes, given time includes additional operations for filling components.

The prepared self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties is used for the manufacture of openwork products by pouring into molds.

Examples of the composition of the resulting self-compacting, extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, manufactured by the claimed method, are given in Table 1.

1. A method for preparing a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high fluidity properties, which consists of mixing the components of the concrete mixture until the required fluidity is obtained, characterized in that the mixing of the components of the fiber-reinforced concrete mixture is carried out sequentially, and initially water and a hyperplasticizer are mixed in the mixer, then add cement, microsilica, stone flour and mix the mixture for 2-3 minutes, after which sand and fiber are added and mixed for 2-3 minutes until a fiber-reinforced concrete mixture is obtained containing, wt.%:

2. Method according to claim 1, characterized in that total time preparation of the concrete mixture ranges from 12 to 15 minutes.

3. A method for manufacturing products in molds from a fiber-reinforced concrete mixture prepared by the method according to claims 1, 2, which consists in feeding the mixture into the molds and subsequent heat treatment in a steaming chamber, and initially a thin layer of water is sprayed onto the inner, working surface of the mold, after filling the mold with the mixture spray a thin layer of water on its surface and cover the mold with a technological tray.

4. The method according to claim 3, characterized in that the mixture is fed into the molds sequentially, covering the filled form on top with a technological pallet; after installing the technological pallet, the product manufacturing process is repeated many times, installing the next mold on the technological pallet above the previous one and filling it.

Similar patents:

The invention relates to the production of building materials and can be used to produce concrete building products subjected to heat and moisture treatment during hardening for civil and industrial construction.

The invention relates to structural materials and can be used in various industries, for example in road and civil engineering. The technical result consists in increasing the crack resistance, strength, and resistance of the micro-reinforcing component to the aggressive alkaline environment of cement stone.

The object of the present invention is a pre-dry cementitious mixture containing, in wt.%: Portland cement clinker with a Blaine specific surface area of 4500 to 9500 cm2/g, preferably from 5500 to 8000 cm2/g, the minimum amount of said clinker in mass percent relative to the total mass of the pre-mixture is determined by the following formula (I): [-6.10-3×SSBk]+75, in which SSBk is the Blaine specific surface area expressed in cm2/g; fly ash; at least one alkali metal sulfate, wherein the amount of alkali metal sulfate is determined such that the amount of equivalent Na2O in the pre-mixture is greater than or equal to 5 wt.% based on the weight of the fly ash; at least one source of SO3 in such an amount that the amount of SO3 in the premix is greater than or equal to 2 wt.% relative to the weight of Portland cement clinker; additional materials having a Dv90 less than or equal to 200 μm, which are selected from limestone powders, wherein the amount of clinker + amount of fly ash is greater than or equal to 75 wt.%, preferably 78 wt.% relative to the total weight of the premix; in this case, the total amount of clinker in the preliminary mixture is strictly less than 60 wt.% relative to the total mass of the preliminary mixture.

The invention relates to the building materials industry. The raw material mixture for producing artificial rock includes, wt.%: Portland cement 26-30, quartz sand 48.44-56.9, water 16-20, fibrous metal ceramics 1.0-1.5, phenylethoxysiloxane 0.06-0.1 .

The invention relates to the building materials industry, in particular to the production of concrete wall blocks. The concrete mixture contains, wt.%: Portland cement 25.0-27.0; characterized by granulometric composition, wt.%: particles larger than 0.63 mm, but smaller than 1 mm - 0.2; larger than 0.315 mm, but smaller than 0.63 mm - 4.8; larger than 0.14 mm, but smaller than 0.315 mm - 62; finer than 0.14 mm - 33 ash and slag filler 15.0-19.0; crushed and sifted through mesh No. 10 slag pumice with a density of 0.4-1.6 g/cm3 30.3-34.3; aluminum powder 0.1-0.2; superplasticizer S-3 0.5-0.6; water 23.0-25.0.

The invention relates to the field of production of artificial materials that imitate natural ones. Raw mixture for the manufacture of material imitating natural stone, including crushed mica and liquid glass, additionally includes water, white Portland cement, quartz sand, phthalocyanine green pigment or phthalocyanine blue pigment in the following ratio of components, wt.%: mica crushed and sifted through a No. 5 mesh 35.0-40.0, liquid glass 3.0-5 ,0, water 16.0-18.0, white Portland cement 27.0-31.0, quartz sand 10.7-13.9, phthalocyanine green pigment or phthalocyanine blue pigment 0.1-0.3. // 2530816

The invention relates to the composition of a raw material mixture for the production of building materials, in particular porous artificial products, and can be used in the production of granular thermal insulation material and particularly lightweight aggregate for concrete. The raw material mixture for producing granular thermal insulation material contains, wt.%: microsilica 33.5-45, ash and slag mixture 3.0-14.5, apatite-nepheline ore enrichment waste 25-30, sodium hydroxide (in terms of Na2O) 22- 27, ammonium bicarbonate 0.5-1.5. The invention is developed in dependent clauses. The technical result is increasing the strength of granular heat-insulating material while reducing its water absorption, recycling technogenic waste. 3 salary files, 1 table.

The present invention relates to the building materials industry and is used for the manufacture of concrete products: highly artistic openwork fences and gratings, pillars, thin paving slabs and curb stones, thin-walled tiles for internal and external cladding of buildings and structures, decorative products and small architectural forms. The method for preparing a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture consists of sequential mixing of the components until a mixture with the required fluidity is obtained. Initially, water and a hyperplasticizer are mixed in the mixer, then cement, microsilica, stone flour are poured in and the mixture is mixed for 2-3 minutes, after which sand and fiber are added and mixed for 2-3 minutes. A self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties is obtained, which contains the following components: Portland cement PC500D0, sand of fractions from 0.125 to 0.63, hyperplasticizer, fibers, microsilica, stone flour, strength gain accelerator and water. The method of manufacturing concrete products in molds consists of preparing a concrete mixture, feeding the mixture into the molds and then storing it in a steaming chamber. The inner, working surface of the mold is treated with a thin layer of water, then a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties is poured into the mold. After filling the mold, spray a thin layer of water onto the surface of the mixture and cover the mold with a technological tray. The technical result is the production of a self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, high strength characteristics, low cost and allowing the production of openwork products. 2 n. and 2 salary f-ly, 1 table., 3 ill.

The disadvantage of this solution is the need to use various equipment for mixing the mixture components and subsequent compaction operations, which complicates and increases the cost of the technology. In addition, when using this method it is impossible to obtain products with thin and openwork elements.

A known composition for the preparation of self-compacting concrete contains:

100 wt. parts of cement,

5-25 wt. parts of ultra-small particles of calcium carbonate and white soot, and the white soot content is no more than 15 wt. parts;

0.1-10 wt. antifoam parts;

0.1-10 wt. parts of superplasticizer;

15-24 wt. fiber parts;

10-30 wt. parts of water.

The search showed that no solutions were found that would ensure the production of reaction-powder self-compacting concrete.

The disadvantage of this method is the high consumption of cement to prepare 1 m3 of the mixture, which entails an increase in the cost of the concrete mixture and products made from it due to the increased consumption of other components. In addition, the method of using the resulting concrete described in the invention does not provide any information on how, for example, artistic openwork and thin-walled concrete products can be produced.

There are widely known methods for manufacturing various concrete products, when concrete poured into a mold is subsequently subjected to vibration compaction.

However, using such known methods it is impossible to obtain artistic, openwork and thin-walled concrete products.

The second task is to increase the strength characteristics at one day of age with optimal workability of the mixture and improve the decorative properties of the front surfaces of concrete products.

The total time for preparing the concrete mixture is from 12 to 15 minutes.

The second task is solved due to the fact that a method has been developed for manufacturing products in molds from a fiber-reinforced concrete mixture prepared in the manner described above, which consists of feeding the mixture into the molds and subsequent curing, and initially a thin layer of water is sprayed onto the inner, working surface of the mold, and After filling the mold with the mixture, spray a thin layer of water on its surface and cover the mold with a technological tray.

Preliminary wetting of the mold with a thin layer of water and the final operation of spraying a thin layer of water on the surface of the poured fiber-reinforced concrete mixture, covering the mold with concrete with the next technological pallet in order to create a sealed chamber for better maturation of concrete allows you to eliminate the appearance of air pores from trapped air and achieve high quality of the front surface of products , reduce the evaporation of water from hardening concrete and increase the strength characteristics of the resulting products.

The number of molds poured simultaneously is selected based on the volume of the resulting self-compacting, especially high-strength reaction-powder fiber-reinforced concrete mixture.

Advantages of this technology and the concrete used:

Use of sand size modulus fr. 0.125-0.63;

Absence of coarse aggregate in the concrete mixture;

Possibility of manufacturing concrete products with thin and openwork elements;

Ideal surface of concrete products;

Possibility of manufacturing products with a given surface roughness and texture;

High grade concrete compressive strength, not less than M1000;

High grade concrete bending strength, not less than Ptb100;

The present invention is explained in more detail below with the help of non-limiting examples.

Fig. 1 (a, b) - diagram of the manufacture of products - pouring the resulting fiber-reinforced concrete into molds;

Fig. 2 is a top view of the product obtained using the claimed invention.

First, all components of the mixture are weighed. Then a measured amount of water and hyperplasticizer is poured into the mixer. After which the mixer is turned on. During the process of mixing water and hyperplasticizer, the following components of the mixture are sequentially poured in: cement, microsilica, stone flour. If necessary, iron oxide pigments can be added to color concrete in bulk. After introducing these components into the mixer, the resulting suspension is stirred for 2 to 3 minutes.