The article contains the results of verification of the finite element design model of work on axial compression of reinforced concrete structures with combined reinforcement. Structures with combined reinforcement (with non-removable steel-fiber concrete formwork) are widely used in the construction of nuclear power plant structures. Steel fiber reinforced concrete, in comparison with heavy concrete, has increased strength and deformation characteristics, due to which it performs the function of a bearing element that perceives compressive and tensile forces. The study of the joint work of steel fiber concrete and heavy concrete is a promising area of research. The developed finite element model of a reinforced concrete structure with a fixed steel-reinforced concrete formwork with a high degree of reliability allows us to determine the stress-strain state, the redistribution of forces between the cross-section elements and the parameters of cracking during loading. The described modeling technique is recommended to be used in the study of the operation of such structures.

Keywords: NPP, nonremoveale formwork, structural testing, Ansys, stress-strain state diagram, steel fiber reinforced concrete, finite element method

The article considers the problem of continuous monitoring of the concentration of dust flow in air ducts at enterprises in the production of building materials. A spectral-timbre methodology for estimating dust concentration based on the analysis of acoustic emission signals is proposed. Two stages of adaptation of the simplified assessment of dust concentration on the bench model and in production conditions were carried out. In the process of adaptation, a piezoceramic sensor is used, an acoustic signal from which using a preamplifier is fed to a recording device called potentiometer with a circular daily diagram . The reference weight method was used to measure the actual dust concentration and simultaneously record the readings of an adapting dust meter.

Keywords: building materials, dust concentration, dust measuring equipment, acoustic methodology, acoustic emission signals, Fourier spectrum

The article discusses the various stages of the study of quarry sand as a component of the cement-sand mixture. Two large-scale stages are designated: drying and sieving. The drying stage for different layers (upper, middle, lower) of quarry sand is given. The results of moisture content of sand weighing from 100 to 5000 g for different layers are given. The screening stage for various layers of quarry sand is given. The granulometric (grain) composition of various layers of quarry sand was determined experimentally according to the normative methodology. The results of partial and total residuals for each layer of sand are given. Size moduli are calculated for different layers of sand. The equipment used for drying and screening quarry sand is illustrated. The experimentally theoretical necessity of the preliminary stages of preparation (drying and sifting) of quarry sand before using it as an integral part of the cement-sand mixture for the production of bricks has been confirmed experimentally.

Keywords: quarry sand, drying, drying, sifting, screening, cement-sand mixture, humidity, granulometric composition, particle size modulus

An analysis of existing ceramic materials for high-temperature thermal insulation is presented. The possibility of obtaining a composite based on zeolite-containing raw materials from the Sakhaptinsky deposit with additives for thermal insulation of industrial aggregates is shown. The results of the effect of additives (clay, microsilica, burnable additives and foam-forming emulsion) on the physical-mechanical and firing properties of the resulting products are presented. The main characteristics of the resulting porous ceramics were studied and the optimal limits for the use of the additives used were determined in accordance with the requirements of GOST 2694-78 for the analogical foam-diatomite brick. The effect of clay content in composites on the density, strength and additional linear shrinkage of samples was determined.An optimal composition has been obtained containing microsilica and burnable additives (sawdust) in the manufacture of porous ceramics used for high-temperature thermal insulation with the lowest density and appropriating the requirements of GOST for strength and additional linear shrinkage.

Keywords: zeolite, clay,microsilica, foam-forming emulsion, burnable additives, chemical composition, firing properties, physico-mechanical properties, porous ceramics, waste products, high temperature insulation

The article discusses the various proportions of the components of the cement-sand mixture for the production of bricks for the construction of private houses. Particular attention is paid to the values ​​of the draft of the cone, as one of the indicators of the mixture. Tables are given with a description of the different composition of the mixture for each component. The results of an experiment to study the effect of different ratios of components are presented. The equipment for manual and automatic molding and creation of finished products from the resulting mixture is illustrated. A conclusion is given on the possibility of using a specific mixture in the production of bricks.

Keywords: brick, cement, sand, water, cement-sand mixture, cement mortar, water-cement ratio, composition selection, construction, production

The article considers the possibilities of using a large fraction of coal industry enrichment waste in road construction. The use of waste rock as a large aggregate in the composition of road concrete is proposed, because the enrichment waste is not disposed of properly, but is sent to the tailings dump. These dumps occupy large areas of land, thereby causing damage to the environment. The fractional composition of coal waste from the enrichment of the Gukovo-Zverevsky coal-bearing area is analyzed. From the results of sieving, it was seen that the structural composition satisfies the size of the fractions of a large aggregate for the concrete mixture. Analytical studies of the composition of the concrete coating were carried out. Based on the analysis of the composition of the concrete mixture, we came to the conclusion that tailings waste can be used as a major substitute. A comparative characteristic of the requirements put forward for the resulting mixture is presented. In our work, one of the main qualities of the road concrete pavement was tested - strength. The results of experimental strength tests of control samples of concrete with various types of aggregate are presented. Based on the results obtained, it is possible to draw a positive conclusion about the possibility of using enrichment waste as a large aggregate of concrete mixture in road construction according to technical and economic criteria.

Keywords: road construction, concrete mix, enrichment waste, coal rock

The results of studies of the effect of mineral additives of natural and man-made origin on some properties of fine-aggregate concrete with the introduction of a mineral additive from 10 to 25% of the cement weight instead of either a part of cement with an increase in the value of W/ C, or a part of sand with a constant value of the value of W / C are presented. A slight, up to 3%, change in the average density of concrete was revealed. A decrease in the E-modulus from 4 to 14% was recorded when replacing a part of cement, while an increase in the flexural strength, depending on the dosage, was up to 26% (marshallite) and 6% (chemical water treatment sludge), and a decrease in the compressive strength was from 10 to 22%. When replacing part of the sand, an increase of up to 10% of the E-modulus, the flexural strength from 19 to 38% (marshallite) and up to 11% (chemical water treatment sludge) was recorded. The increase in the compressive strength, depending on the type and dosage of the additive, ranged from 8 to 20%. No significant effect of additives on the porosity of cement stone was revealed.

Keywords: mineral additive, fine-aggregate concrete, flexural strength, E-modulus, shrinkage, water absorption

The active use in the production of building materials of waste after the renovation of housing is a relevant and promising direction. the load on logistics for the supply of inert materials is reduced, landfills and waste storage sites are being destroyed, and the cost of building materials from recycled materials is being reduced. The use of recycled clay bricks allows to solve the problem of solid waste disposal, but also to reduce the environmental damage caused to the environment by mankind from the excessive development of natural resources. Finely ground brick cullet has pozzolanic properties and can be used as an additive in a cement mixture, and a large fraction is used in aggregates of cement compositions.

Keywords: Сlay brick scrap, renovation, preparation, pozzolanic activity, hydraulic activity, binder, hardening, aggregate, mortar, strength

The increasing problem of the formation of ash dumps in the Rostov region dictates the need to search for environmentally friendly methods of waste disposal in the heat and power sector. In this article, the ash and slag waste of the Novocherkassk GRES is considered. We analyzed the chemical and fractional compositions of the ash-slag mixture formed at a coal-fired thermal power plant and proposed the use of ash waste with a size of 10-100 microns in road construction as a micro-filler. To study the strength of the road surface using ash microparticles, we manufactured and tested cubes of modified concrete mixture for compression using a press machine. The obtained result showed that the use of ash as a micro-filler in concrete does not affect its strength in any way. The tests of control samples with the use of ash wastes showed an improvement in the water resistance and frost resistance of concrete while maintaining its strength.

Keywords: ash and slag waste, micro-filler, concrete mix, road construction

The article considers the possibility of increasing the resistance in sulfate environments of concrete composites based on cement raw mixtures modified with a slag mineral component and a complex superplasticizer. The method of research and modeling of the nature of the impact of an aggressive environment on composites proves the prospects of the technology of chemicalization of cement concretes for the manufacture of durable building structures based on them.

Keywords: sulfate environment, cement concrete, corrosion resistance, chemicalization, composite, environmental impact modeling

The practical application of NIPU based on epoxy-amine compositions and five-membered CCs in coatings, sealants, adhesives, etc. was largely developed back in the USSR by O. Figovsky &V. Stroganov. Opportunities for optimizing the production of the key component of NIPU, cyclic carbonate, using carbon dioxide are considered. The article discusses sustainable synthesis routes for NIPC for industrial applications. An overview of solutions for the production of foam materials based on non-isocyanate polyurethanes is given.

Keywords: nonisocyanate polyurethanes, oligomeric cyclocarbonates, green solutions

The results of studies of the influence of various hardening conditions, incl. simulating conditions in the center of massive monolithic structures, for compressive and tensile strength, initial modulus of elasticity, hardening kinetics of self-compacting concrete of classes from B25 to B55. A classification of concretes according to the hardening kinetics is proposed, using as a criterion the time to reach a certain level from the design compressive strength under normal hardening conditions. The invariance of the dependence of the initial modulus of elasticity of the investigated concretes on the compressive strength on the age and type of concrete is established. A certain difference between the dependence "initial modulus of elasticity - ultimate compressive strength" and a lag in the rate of increase in tensile strength from the rate of increase in compressive strength of the studied concretes in the early period of hardening relative to traditional concretes of vibration compaction were revealed. It is shown that in the early period of hardening the studied concretes are characterized by a higher level of the conditional crack resistance criterion E0/Rt, which indicates to a certain extent a higher fragility of the studied concretes in this period.

Keywords: self-compacting concrete, compressive and tensile strength, hardening kinetics, modulus of elasticity, crack resistance criterion

The article presents the results of experimental studies. The optimal time of dispersion of the mixing water together with the nano-additive has been determined. The results of experiments to determine the effect of carbon nanotubes and plasticizer on fine-grained concrete are also presented. Strength characteristics were determined for the studied compositions. Based on the data obtained, the effect of the dispersion time was determined, as well as the effect of the combined use of the SikaVC 5-500 plasticizer and carbon nanotubes "Taunit-M".

Keywords: fine-grained concrete, carbon nanotubes, ultrasonic dispersion, plasticizer

The construction of a Polar gas turbine power plant is carried out on permafrost soils. Features of the construction of reinforced concrete structures of foundations and other elements in the permafrost zone implies high requirements for strength, density and frost resistance. A new composition of the concrete mixture with improved physical and mechanical properties is proposed. Superplasticizing additives and production waste are used in the composition of the concrete mixture.

Keywords: foundation, permafrost, borehole piles, superplasticizer, sulfuric acid sludge, concrete mix, strength, frost resistance

The influence of redispersible polymer powders on the change in the properties of building mortars after holding at high temperature in accordance with GOST R 56387-2018 has been studied. An increase in the compressive strength by 10 – 15% was revealed at a dosage of RPP 2 – 3%. It was found that the introduction of an air-entrapping admixture into the composition has a negligible, up to 5%, negative effect on increasing the compressive strength. The increase in the flexural strength after holding at high temperature was 1.5 – 1.8 times. The decrease in the E-modulus practically does not depend on the dosage of RPP. After holding at high temperature, the E-modulus was 0.8 – 0.84 relative to normal hardening conditions. A decrease in the adhesion strength to the concrete base to values of 0.39 – 0.71 relative to normal hardening conditions was revealed. It is noted that the decrease in adhesion strength significantly depends on prescription factors, with the exception of formulations containing an air-entrapping additive, in which there is practically no decrease in adhesion strength after holding at high temperature.

Keywords: redispersible polymer powders, adhesion strength, E-modulus, compressive and flexural strength, high temperature

Results of research of waste ash-and-slag mixture being a waste product of thermal power plants are presented. Effectiveness of its use as a mineral component of a complex organic-mineral additive is shown. Methodology of mathematical modeling and optimization of properties of concrete modified by complex organomineral additive allowing to reduce cement consumption by 20% without loss of concrete strength is presented.

Keywords: оrganomineral additives, industrial waste, mathematical modelling, cement saving

The article proposes new compositions of a fast-hardening concrete mixture using Portland cement, fine and coarse aggregates, basalt fiber, a complex modifying additive including acetone-formaldehyde resins and magnesium chloride (bischofite). The results of scientific and experimental studies are presented and the influence of the proposed additives on the formation of the structure, rheological and physico-mechanical properties of fast-hardening concrete is determined. Analysis of the test results showed that the proposed formulations, including a complex additive and basalt fiber, contributed to a decrease in the water-cement ratio, increased mobility of the mixture and increased strength of hardened concrete in the early and final hardening periods.

Keywords: concretes, oil and gas storage, modifying additives, fiber, mobility, setting time, strength

This article discusses strength testing of welded joints by pulling joint materials using an automated material testing system.

Keywords: YAG laser welding, packaging of photonic devices, laser processing of materials.