The reliability (safety) of the designed structures is ensured by using the design value of the bearing capacity, taking into account the uncertainty (variability, error) of the bearing capacity. Uncertainty is taken into account by means of a probabilistic model, which is represented as a distribution law with statistical parameters included in it. The most important and frequently used statistical parameters are the mean value and coefficient of variation. Determining the coefficient of variation for the bearing capacity calculated on the basis of numerical models (computer modeling) is an important task, since existing classical methods cannot be applied. For this reason, the purpose of this article is to develop and study the accuracy of methods for determining the coefficient of variation of the bearing capacity calculated by computer modeling.

The proposed method for determining the coefficient of variation is based on the decomposition of the function into a Taylor series, followed by the use of various numerical differentiation schemes. Verification was performed on generalized nonlinear models of load-bearing capacity, for which an exact solution can be obtained using the Monte Carlo method. The practical implementation of the proposed method is demonstrated on finite element models.

As the results of the performed research, it is possible to identify the actual methods for determining the coefficient of variation of the bearing capacity calculated by computer modeling, and the values of the coefficients of variation for generalized models of the bearing capacity of thin-walled elements, taking into account the loss of local stability of the web and with the subsequent inclusion of the girder flanges in the work.

The value of the coefficient of variation can be most accurately estimated using Taylor series expansion and numerical integration over 3 points, however, this method requires 2N+1 calculations, therefore it can be recommended only for individual verification tasks. As a practical method for estimating the coefficient of variation, Taylor series expansion and numerical integration by 2 points should be used (N+1 calculations are required).

This article uses research results that allow you to get self-healing building materials based on mineral binders. This happens by adding microcontainers to dissolved mixtures, which use nutrients for bacteria with urease activity, which produce calcium carbonate, which fills microdefects in the material. The research results include the use of active forming bacteria, as well as their effect on various properties of modified mortars. To obtain soluble mixtures with different pH values, Portland cement and gypsum binder were used. Indicators of their active work. In this work, the dependence of the aquatic environment on the concentration of biomass in the dissolved building mixture, the dependence on the aquatic environment and microorganisms is shown. The results are associated with the presence of biological surfactants in bacterial cells, which have a significant effect on the rheological properties of cement-sand mortars. A change in the setting time and strength characteristics of cement-sand mortars at various cell concentrations

The prospects and problems of multicomponent multilevel optimization of the dispersed composition of self-compacting concrete are considered with the aim of significantly increasing its construction and technical properties, with a minimum content of binder. Theoretical and practical principles have been developed for the design of disperse-particle size distribution of self-compacting concrete mixtures for high-strength concrete, in which various types of dispersed mineral modifiers (MM) are used, including fly ash of thermal power plants. Effective MMs for self-compacting concrete mixtures are differently dispersed granular blast furnace slag, fly ash of thermal power plants and silica fume, which create a dense packing structure of particles of a multicomponent binder with a low degree of disorder and ensure a decrease in the consumption of Portland cement in concrete up to 50% and higher. With such a choice of the type and parameters of MM, self-compacting concrete mixtures are characterized by lower water content, high viscosity and a low level of ultimate shear stress, ensuring its high-quality compaction. To study the properties and structure of concrete, quartz sand with Mk -2.58, granite crushed stone fr. 5-10 mm, Portland cement of class CEM I 52.5 N, finely dispersed granulated blast furnace slag, fly ash of thermal power plants, micro-silica and superplasticizer Glenium 430. For a uniform course of the pozzolanic reaction, a finely dispersed cement fraction was used in each micro-volume. Research methods: the shape and size of the dispersed particles of the components were determined by a laser analyzer, the mobility of the concrete mix in accordance with GOST 10181-2014, the compressive strength of concrete in accordance with GOST 10180-2012. The structure of the cement stone was studied by thermographic and X-ray phase analysis methods.

The present study evaluated the combined effects of organic-mineral additive based on a superplasticizer SR 5000F and the active mineral additive fly ash, blast furnace slag and silica fume SF-90 on properties of foam concrete. The calculation of mixture proportions of foam concrete is applied by the absolute volume method. Besides, the compressive strength and flexural strength of foam concrete are determined by Russian standard GOST 10180-2012. The porosity of the foamed concrete is determined by American standards ASTM C457-1998. The results from experiments show that flexural and compressive strength of the foam concrete obtained respectively, from 0.526 to 1.061 MPa and from 1.69 to 8.22 MPa. The relationship between compressive strength and curing age, compressive and flexural strengths of the FC were also determined in this investigation. The results of this study demonstrated that the use of fly ash and blast furnace slag to replace natural sand could produce foam concrete and environmental protection.

The article discusses the possibility of obtaining composite gypsum binders (СGB) for 3D additive construction technologies. Carbonate-siliceous rock - opoka-like marl (OM), which contains X-ray amorphous substances that determine its hydraulic activity when interacting with Ca (OH) 2 with the formation of low-basic calcium hydrosilicates and other neoplasms, is proposed as an active mineral additive, compacting the micro structure of the hardening matrix and, as a result, increasing the stability of the compositions. The main characteristics of the opoka marl are given. The processes of structure formation of the SHG have their own characteristics. With the participation of OM, Ca (OH) 2 is bound and removed from the reaction sphere. The hydrolysis of clinker minerals is accelerated, while the number of low-basic calcium hydrosilicates of the CSH (B) type increases, which positively affects the initial strength of the hardened CGB.

Powders with the ability to swell are widely used in the building materials industry in the production of wood-polymer composites and elastomers. In this regard, the choice of compatible polymer binders and swellable powder fillers becomes an important task. Such a selection can be carried out using surface tension determined by the OWRK method as an information parameter, taking raw components having close values of the polar and dispersion components, eliminating a possible imbalance of intermolecular forces at the filler-polymer binder interface. However, when using this approach, the problem of obtaining reproducible wetting angles of swellable powders arises - the solution to this problem, in the case of using modern goniometers as measuring equipment, was the goal of this work. It was found that for swellable powder materials (saponite-containing material, wood flour), in comparison with quartz powder, to determine the pseudo-equilibrium contact angle, it is necessary to carry out a corrective change in the position of the baseline by the level of the boundary of the swollen material.

The object of the study is cement composites with active mineral additives. Additives promoting corrosion resistance of composites are considered. Some are active to cement dough, others - to aggressive environments. Additives active to aggressive media can crop out to the surface of composites and react with penetrating media. The results of the research revealed possible mechanisms of physical and chemical interaction of additives with aggressive media. The samples were cured by steaming and under normal conditions. Examples of results of acid resistance study of cement composites with additives are given. The acid resistance of cement stone with the product of cement decay in sulfuric acid was compared with the results obtained in the test of cement stone with 10% marshalite content. And the index of resistance of fine-grained concrete with aggressive additives, with barium chloride and stroncium, was compared with the results of testing concrete without additive and containing diatomite. According to the studies carried out cement stone with marshall has higher initial strength. However, cement stone with the addition of corrosion product has higher strength and resistance after exposure in aggressive media. It has been shown that the corrosion resistance of the steamed cement stone in 2% sulfuric acid solution, both with and without additive, is significantly higher than that of the normal hardening stone.

The article presents the recycling technology of reinforced concrete formed during the renovation program in Moscow city. It is shown that the part of concrete can be recycled to obtain raw materials for self-compacting concrete use, including products of recycling. The products include recycled concrete aggregate 5-10 mm fraction and the filler. It is indicated that the efficient concept of recycling process is sorting of various types of products and removal of contaminants. The sequence of technological operations for dismantling buildings, transportation and recycling of concrete, storing and quality control of the resulting product has been developed. Technological methods that allow to obtain self-compacting concrete mixtures with the use of recycled concrete in concrete plant are suggested.

This paper presents the results of a study of the variability of physico-mechanical and physico-chemical properties, as well as structural features of aluminosilicate technogenic raw materials from wastes of fuel and energy enterprises in the form of various types of ashes as components of bitumen emulsions used in the composition of a hybrid binder (Portland cement - bitumen emulsion) for cement-asphalt concrete. Based on the analysis of the set of characteristics of fuel ashes, the possibility and expediency of their introduction into the composition of bitumen emulsions were determined with the aim of obtaining bitumen layers in the structure of cement-asphalt concrete, allowing to improve its operational characteristics. As a result of the analysis, the most effective diluent additive was identified among the studied technogenic raw materials, which would allow keeping its properties at the stage of introduction into the emulsion, and at the stage of forming the structure of the final composite to provide the desired properties.

An approach to the study of the mechanism of deformation of composite materials in tension, based on the use of methods for analyzing curves "σ - ε", fixed with modern test equipment with a high frequency of reading (0,01 sec.). The change in time series of stress increase of the epoxy polymer depending on the step of fixing the readings is analyzed. It was found that with an increase in the step from 0,01 to 0,16 seconds, there is a structuring of the time curve, which allows us to identify zones with different patterns of accumulation of structural defects. Based on the analysis of the destruction of a solid body as a discrete-continuous process, the coordinates of the most "critical" points of the deformation curves are determined, which are characterized by the smallest negative indicators of stress increase over the previous time interval of 0,16 seconds, containing 2 ⁴ experimental points. An algorithm for estimating the rate of damage accumulation in the structure of polymer materials is proposed based on the analysis of stress increase with an increase in the elongation under tension. It is shown that the number of failures determined from the analysis of deformation curves recorded with high frequency allows us to quantify the critical level of defects that lead to the destruction of composites.

The paper notes the relevance of the development of gypsum materials modified with foam-ceramic granules. A review of the literature has shown that currently foam ceramics are used mainly in concrete and cement-based mixtures. The closest analog of foam-ceramic granules is foam glass, which is already widely used in the production of plaster mixes and gypsum-based screeds, so the authors do not see any obstacles to the use of foam-ceramic in their composition. Such an approach could reduce production and raw material costs, since foam ceramics require lower temperatures when they are heated and are produced primarily from mining waste.

The article presents the results of a study of changes in the structure and properties of concrete reinforced with low-modulus synthetic microfibres after exposure to high temperatures. The analysis of the causes of the phenomenon of explosive destruction in concrete during heating is carried out. A review of modern methods of increasing the fire resistance of building structures, including possible ways to prevent their explosive destruction in the event of a fire, is performed. It is shown that synthetic microfiber burns out at a temperature close to 400 ° C, forming additional porosity for water to escape in the form of steam from concrete. With a further increase in temperature to 600 ° C, a significant number of cracks are formed that increases the defectiveness of the structure and reduces the strength of fiber concrete. Comparison of the water resistance of concrete and fiber-reinforced concrete samples after temperature exposure by the filtration coefficient is carried out. The mechanism of increasing the resistance of concrete to high temperatures and explosive destruction upon heating as a result of reinforcing with low-modulus microfibers has been clarified.

Innovative development of technologies of construction composite materials directly depends on understanding a mechanism of water binding in the mineral system. Aqua-complex [2TO ₃ ─ H ₂ O ─ M ⁿ⁺ M ^m+ O` <sub>4</sub> ] (where T is, mostly, Si and other four-valent cations: C, Ti, etc., M <sup>n+</sup> is uni- and bivalent cations: Na, Fe <sup>2+</sup> , etc., M <sup>m+</sup> is multivalent cations: Al, Fe <sup>3+</sup> , etc., O` is O and other volatile elements: Cl, S, etc.) is a solution to the problem. Aqua-complex was first found as a result of studying the problem of water ̶ natural mineral matter binding. Further, the role of aqua-complex as a law of evolution of the terrestrial matter was justified by the complex of geological-mineralogical and experimental data. Verification of the concept of aqua-complex, besides geological sciences, was made based on various natural sciences (pedology and others), as well as practical applications. The concept of aqua-complex unravels the nature of cement binding properties and gives an answer to the key problem of construction material science: why as a result of water sealing of a system of fine-dispersed mineral components (C - S system) their consolidation and formation of monolith, an artificial analogue of rock matter, occurs? The knowledge of the nature of solidification in the C ─ S ─ H system allows as much as possible optimizing the technologies of production of the building materials with the specified properties. This is shown in the case of the development of construction composites based on concrete.

Due to the shortage of high-quality clay raw materials, in many regions of Russia the urgent task of obtaining bricks, especially facing, from rocks with a low content of clay fractions. The problem can be solved by using the semi-dry pressing method. It is recommended to clarify the ceramic crock by introducing finely ground chalk in combination with a reinforcing additive wollastonite. The composition of the mixture was selected by the method of rational planning of the experiment. The introduction of additives in the optimal dosage made it possible to obtain: the cream color of the crock from red-baked clay raw materials with compressive strength of 49.5 MPa and water absorption of 10.5 wt.%. In this case, it is necessary to strictly control the dosage of chalk, as exceeding it above the optimum leads to a decrease in tensile strength and an increase in water absorption. Thus, based on raw materials with a clay particle content of only 6.8 vol. % it is possible to obtain a front ceramic brick with a clarified shard.

The purpose of this work is to study the behavior of activated microsilica in an alkaline environment and the effect of fibers (fibers) on the physical and mechanical characteristics of concrete. The method of microsilica activation in an alkaline medium and stabilization of fine particles by superplasticizer is proposed. For the comparative analysis of the results, in the developed compositions of concrete mixtures were introduced micro-fiber in the form of basalt and polypropylene fiber with consumption from 0.5 to 1% by volume. Testing of specimen prisms of the studied concrete mixtures was carried out with the recommended intensity of loading, fixation and processing of the results. It is established that the samples-prisms of heavy concrete with basalt fiber (BF 0.75%) withstand the maximum load and have a conventional stress intensity factor higher by - 25.91%, bending stress - 25.89% in comparison with the control composition. In relation to samples with polypropylene fibre (PP 0.75%) by 10.85% and 10.87% respectively. The received results of researches of the modified concrete on the basis of application of chemically activated microsilica with microarming fibers possessing the improved physical and mechanical properties and operational indicators, allow recommending it for building of products and designs in heavy conditions of operation.

The criterion for assessing the quality of the pigment may be a detailed characteristic of its dispersion. The dispersion parameters of two grades of pigment titanium dioxide were studied: from an expensive and affordable price range. The method of laser diffraction was used. It has been established that most of the mass (volume) of particles of the studied pigments has sizes outside the effective range from the point of view of scattering power. Pigments have a close number of particles with sizes in the effective range (in the range of 0.19-0.25 microns). The most probable particle size of the cheaper pigment corresponds to the region of the optimum particle size, while that of the expensive pigment is below the optimal values. In both investigated brands of pigment there are nanoparticles with sizes less than 115 nm. Their volumetric (or mass) content is not less than 1.5%; or at least 7% of the total specific surface area of all pigment particles. Studies are needed on the dependences of the durability of pigmented coatings on the presence and content of nanosized particles.

In the manufacture and installation of sulfur-asphalt concrete mixtures, chemical reactions occur, accompanied by the release of toxic gases - hydrogen sulfide and sulfur dioxide. This significantly limits the use of sulfur for the manufacture of sulfur-asphalt concrete. One of solutions for the problem above is adding neutralizing agents into the composition of the sulfur modifying converter. As neutralizing agents sulfur modifying additives chemically interact with hydrogen sulfide and sulfur dioxide to form sparingly soluble or insoluble compounds, such as manganese oxide, zinc oxide, copper oxide, zinc, dolomite, diatomite. The kinetics of hydrogen sulfide gas (H ₂ S) and sulfur dioxide (SO ₂ ) emissions are presented as well as their dependences on the type of neutralizer. A comparative analysis of the intensity of toxic gas emission from a sulfur-bitumen binder is carried out. A description is given of an experimental setup for determining changes in the intensity of toxic gas evolution and the effect of neutralizers. Studies of the advantages of sulfur-asphalt concrete with toxic gas emission neutralizers show that their use reduces the amount of emission of these gases and improves the environmental problem of using sulfur-asphalt concrete.