The article presents dependencies between deformation characteristics of SFRC with a high-strength cement-sand matrix from the type of steel fiber and its volumetric content. It was found that the introduction of fiber imparts plasticity to the matrix. Plasticity depends more on the type of fiber than on its amount per unit volume. Full deformation diagrams of steel fiber reinforced concrete have a descending branch, in contrast to the matrix diagram. The introduction of steel fiber increases the deformations corresponding to the ultimate tensile strength by no more than 75%. Deformations of the descending branch of the diagram, depend on the type of fiber, characterizing the plastic properties of steel fiber reinforced concrete. At the same time, it essential how fiber ensures the adhesion to the matrix: along its entire length due to its fiber profile or due to the design features of the anchors at its ends.

Keywords: axial tension, complete diagram of deformation of steel fiber reinforced concrete, type of fiber, percentage of fiber reinforcement, ductility, residual strength

Currently, the quality of the microclimate, which ensures comfortable living of people comes to the fore in comparison with energy saving. One consequence of the desire for energy conservation has been increased sealing of window openings, which has disrupted the natural ventilation system and worsened air quality in residential buildings, which is particularly dangerous in the face of increased coronavirus infection. The article justifies the need to replace the reconstruction and overhaul of residential buildings of natural ventilation systems, which do not provide the necessary air exchange in residential buildings with airtight windows, to autonomous mechanical ventilation exhaust systems with the recovery of the heat of the exhaust ventilation air in the conditions of Volgograd..

Keywords: energy conservation, energy efficiency, microclimate quality, natural ventilation, mechanical ventilation with recovery

Creep is a slow plastic (irreversible) deformation of a product under the action of stress created in the material. This article discusses the creep of polymer products. The creep of a material is characterized by the experimental dependence of the deformation resulting from a fixed load on time.

Keywords: material deformation, elastic deformation, highly elastic deformation, polymers, viscous deformation, plastic deformation

This paper reports on the results obtained on the diagnostics of a steam pipeline of a thermal power plant; it analyzes the effect of thermal fatigue on the structure and properties of the 12Kh1MF steel and possible reasons for the emergency destruction of steam pipeline elements before the exhaustion of economic life. Ultrasonic testing and additional heat treatment are proposed to be used for the detection and elimination of structural inhomogeneity in the metal. The applicability of statistical technique to analyzing data on the loading history of a steam pipeline is studied, which enables us to evaluate the damaging effects of loading cycles and to develop a plan of preventive measures, as well as to increase the accuracy of predicting the residual life of steam pipeline elements.

Keywords: metallic structure, diagnostics, degradation, steam pipeline, thermal fatigue, microstructure, mechanical properties, residual life

This article presents the effect of mixing water and mineral additives on the mechanical properties of foam concrete. All materials used in this study are from Vietnam. The effect of water and mineral additives on foam concrete's mechanical properties was studied using the Box-Wilson method. Mechanical properties of foam concrete at the age of 28 days were determined according to GOST 10180-2012. The results obtained are second-order regression equations, which describes the dependence of the compressive and flexural strength of foam concrete on the content of water and mineral additives. The optimal composition of foam concrete mixtures was obtained using materials from Vietnam. Based on the results of this study, in the future, the author will continue to study the properties of foam concrete as thermal insulation properties, water absorption, permeability, modulus of elasticity, structural porosity, etc.

Keywords: blast-furnace slag, foam concrete, compressive strength, flexural strength, optimization

The article presents the results of the analysis of the modern market for the production of precast concrete products and existing technologies for their production, as well as a description of the possible method of modernization of the technological line and the production process. The main goal of the modernization is to eliminate vibrating stations and the use of self-compacting concrete mixes from the production line, which significantly increases the plant's productivity, increases the service life of molds, reduces the production time of the product and reduces financial costs.

Keywords: high-functional concrete, self-compacting concrete, production modernization, road slab, production of reinforced concrete products, conveyor production technology

The concept of competitiveness in the construction sector is considered. The assessment of the competitiveness of the enterprise for the production of construction products was carried out. The ways of increasing competitiveness using the results of SWOT analysis are considered.

Keywords: competitiveness, competitor, construction market, quality, enterprise, SWOT analysis, integral indicator of competitiveness

For the statically indeterminate systems under consideration, there is an optimal ratio between the load-bearing capacity of stretched and out-of-center compressed elements, in which the required reliability will be provided at the lowest value of the mathematical expectation of an external destructive load. It should also be noted that for statically indeterminate systems, the beginning of rebar fluidity is not a sign of destruction, but only indicates the beginning of an intensive redistribution of forces in it. Therefore, the values of C, do not refer to the beginning of the rebar flow, but to the complete exhaustion of the load-bearing capacity. The reliability of statically undetectable systems, including prestressed trusses, is always higher, all other things being equal, than that of statically definable systems.

Keywords: reinforced concrete, reinforced concrete structures, statically indeterminate systems, reliability

The paper studies the applicability ofthe coercive force (Нс) as a parameter for measuringthe wall thickness ofpipelines,vessels,andother metallic structuresthroughnonmagnetic insulationduring material degradation undercorrosion conditions. A procedure is developedfor remote inspectionof metallic structures atsites of maximum corrosion rateby the coercimetricmethod,withoutbreaking the insulationandstopping the operation ofthe object being tested.The effects of metal thickness, the size ofthe poles of the magnetizer, andthe thickness of non-ferromagneticinsulationon the absoluteand relativevalues of the coercive force are comparatively analyzed. The application of theproposed relative value methodis shown to be able to decrease significantlythe effectof steel composition and structureonthe metal thickness dependence of Нс. The results of measuring the coercive force of differently thick 09G2S steel specimens through non magnetic insulation are presented, as well as the behavior of the relative values of the coercive forceas dependent onmetal and insulation thickness.Foridentical metal thicknesses, the absolute values of the coercive force of different steels may differby a factor of 10 ormore, whereasthe difference in the relative values of Нс with equally decreasing metal thickness does not exceed 15%. The developedtechnique isinsensitivetothe misalignment of the outer and innermetal surfaces,and itenablesthe thickness oflow-alloysteels like 09G2Sto be measured witha relative error of 10%.

Keywords: metallic structure, diagnostics, degradation, corrosion, coercive force, thickness measurement, nonmagnetic insulation

The article discusses the prospects for the development of the combined technology of expanded fiber gypsum material. Based on the literature data, the optimal boundaries of the components were determined. To obtain the optimal composition, complete two-factor experiments were performed with changes in each factor at three levels. The results of the tests were obtained, on the basis of which regression equations were constructed, allowing to predict the characteristics of the resulting material, for the selection of the optimal composition.

Keywords: expanded gypsum, fibrogyps, fiber, strength, density

The results of the development of a set of indicators for the quality of construction products on the example of a reinforced concrete pile are presented. The analysis of the requirements of regulatory documentation for the evaluation of aesthetic indicators of the product is carried out. A solution to the dispute between the Supplier and the Customer on the issue of assessing the quality of the concrete surface is proposed.

Keywords: quality management, improving competitiveness, consumer requirements, quality indicators, technical level, aesthetic indicators, construction

" This article deals with the problem of fixing bulk and weak soils, leveling the deformation properties of soils during their water saturation. The technology of injecting the fixing cement-sand solution, closed with a solution of liquid glass, was described on the example of fixing the base under the foundations of a residential building under construction in the floodplain zone of the Taganrog Bay on Kruysa Street.

Keywords: structurally unstable soil, hydrogeological risk, floodplain zone, foundation consolidation, cementation, liquid glass, cement-sand mortar, foundation plate, deformation, ground water

The article is devoted to solving the issues that arise when choosing the issues of materials for use on the sites of oil fields. The basic concepts of composite materials are revealed. The article presents the prerequisites for the introduction of composite materials for the oil and gas industry. The examples of structures using CM that are used today are presented. The advantages of using a composite material are revealed. An overview of the problems of its implementation in Russia is made. The advantages for construction work when using this material are determined. The minuses of CM, methods of dealing with their flaws are also considered. A detailed analysis of the modern composite materials market takes place.

Keywords: composites, construction and installation works, automation, composite materials, overpasses, fiberglass

The possibilities of using volcanic tuff as an additive in pressed cement-mineral composites intended for road construction are studied. The influence of low-modulus mineral additives of trepel, granulated blast furnace slag and volcanic tuff on the physical and mechanical properties of hardened composites is studied. The rational compositions of the molding masses of the optimal structure of cement-mineral composites providing the improvement of physical and mechanical properties are determined.

Keywords: small-piece pressed products, hard pressing, cement-mineral composites, paving slabs, screenings, volcanic tuff, trepel, granulated blast furnace slag, structure-forming additive, decaying strength

The article deals with some of the most common waste from the construction industry. These are waste generated as a result of the construction of buildings and structures, concrete scrap. At the moment in Moscow in 2018, a programme of renovation, demolition of old housing, which estimates the amount of concrete scrap will amount to more than 14 million m3. The most effective way of recycling is using waste concrete scrap including eliminations of crushing in the manufacture of concrete. The problems of processing concrete scrap associated with the accumulation of a large number of screenings of concrete scrap, which is actually not used anywhere, are considered. Their number increases very much every year. As a result of the study, the chemical and mineralogical composition of ground concrete scrap was determined, as well as the grinding was performed up to Sud = 500 m2/kg. The possibility of using these ground wastes of concrete scrap (MOBL) as an active mineral additive (AMA) for the production of cement-sand solutions is considered. Due to the significant content of silica in these wastes in crystalline and amorphous form, these wastes can be classified as silica-containing. The kinetics of hardening of cement-sand solutions using active mineral additive was studied, histograms were constructed and conclusions were formulated.

Keywords: waste, construction industry, renovation, old place, concrete scrap, recycling, active mineral additive, mineralogical composition, cement-sand mortar, kinetics of hardening

In recent years, studies have begun on the possibility of using anhydrite binders. However, the slow hardening makes it difficult to use this binder for residential and civil construction. The elimination of these difficulties is possible as a result of a deep and comprehensive study of the hardening process of anhydrite binder and the properties of the resulting stone, will make it possible to develop a technology for the manufacture of various building structures based on this binder.

Keywords: Investigation of the properties of a material based on a modified anhydrite binder

In connection with the increase in production activity in the winter and in remote areas, in regions close to the regions of the Far North, the use of new building materials is required. One of the most common building materials is concrete. This article describes an experimental study of the concrete substitute "HILST" for compliance with the manufacturer's declared characteristics: the ability to mix, hardening at room temperature and under adverse conditions.

Keywords: building materials, concrete, concrete substitute, HILST, mixing, experiment, adhesion, building chemistry, hydrophobicity, foundation

According to regulatory requirements, the Khakassia Republic is characterized by high seismicity, and therefore reliability and safety requirements are imposed on buildings and structures in accordance with SP 14.13330.2014 “Construction in seismic regions”. It is necessary to significantly reduce or eliminate the likelihood of an emergency, to ensure the necessary margin of safety and durability of buildings. It is possible to achieve such a multifaceted effect, including through the introduction of construction technologies using fiber-reinforced concrete. The experience of Russian and foreign researchers shows that the use of fiber-reinforced concrete in various structures makes it possible to achieve higher tensile strength, no shrinkage and resistance to cracking, as well as high impact strength and plasticity. In this regard, the study of the possibility of using fiber-reinforced concrete in the conditions of the Khakassia Republic is relevant. The purpose of this work is to study structures using fiber-reinforced concrete based on basalt fiber, which has increased strength, as well as to analyze the stress-strain state of models of various structures. The article presents the results of determining the optimal percentage of concrete reinforcement with basalt fiber based on the study of the kinetics of changes in strength in compression and bending. The paper presents the dependences of changes in strength and shrinkage deformations on the percentage of reinforcement. It is shown that concretes with 2% fiber content are characterized by the best performance. It is noted that an increase in the percentage of fiber reinforcement does not always lead to an increase in strength due to the uneven distribution of fiber throughout the volume. The authors investigated the stress-strain state of bending elements (slabs, beams) based on fiber-reinforced concrete. It is shown that when using basalt fiber, there is a decrease in the percentage of reinforcement with working reinforcement of reinforced concrete elements to 26–57 %.

Keywords: Fiber concrete, basalt fiber, percentage of reinforcement, bending element, shrinkage, deformation, stress-strain state, compressive strength, flexural strength, steel economy

This article discusses the use of local additives and waste for the production of building materials and products. This topic is very relevant at the present time, since a large amount of waste has been collected all over the world, which occupies huge areas of fertile land and pollutes the environment around us, and we also considered the issue of increasing the quality of concrete by chemicalization.

Keywords: construction, building materials, waste, additives, environmental pollution, ecology, new technology

The work was carried out due to the fact that the regulatory documents used in the design of structures operating at elevated and high temperatures do not take into account the peculiarities of the mineral composition and structure of concrete aggregates. This is a disadvantage of these documents, since the mineral composition and structure of aggregates can differ significantly even for materials of the same name, which can significantly affect the thermal changes in concrete. Due to the impossibility of experimentally investigating all the variety of concretes based on aggregates of various mineral composition and structure, a computational and analytical study was carried out in the work on the basis of existing methods for the analytical determination of thermal changes in concretes and their components. On the basis of these methods, the effect on the thermal expansion of concretes of the presence and amount in the aggregates of the most expanding minerals (aragonite, calcite, quartz, cristobalite, potassium feldspars, pyroxenes) and glass, as well as the average size of crystals composing mineral fillers, has been calculated and investigated. Considered are heavy Portland cement concretes on aggregates of limestone, dolomite, granite, syenite, diorite, basalt, diabase, broken clay brick, chamotte and slags. Based on the calculations, it has been established that the values of the thermal change in the volume of concrete, determined according to the normative document SP 27.13330.2017, coincide with the calculated values only for certain combinations of the mineral composition and structure of aggregates in terms of crystal sizes. In other cases, the actual thermal expansion of concrete may be less and more than the values obtained according to SP 27.13330.2017. The regularities of the influence on the thermal expansion of concrete of the content of various minerals and the average size of the crystals of minerals in the aggregates are established.

Keywords: thermal expansion, conventional and heat-resistant concretes, aggregates, minerals, glass, the effect of the mineral composition and structure of aggregates

The use of adhesive joints for reinforcing elements of steel structures is discussed. Adhesive joints provide the least costly way of joining elements of any material without disturbing their structure. Of particular interest is the reinforcement of structures in stretched zones using high-strength fibers such as glass and carbon fibers, as well as polymers reinforced with them. The main problem in this case lies in the peculiarities of the distribution of shear forces along the length of the adhesive layer. The article discusses a way to solve this issue.

Keywords: adhesive bond, adhesive layer, shear strength, analytical solution, finite element method, high strength fiber, carbon fiber, glass fiber

On the territory of the Perm Region there are a large number of deposits of carbonate rocks. Their application in various industries is limited due to the high amount of impurities, so to expand the scope of application of local carbonate rocks, it is proposed to use chemical methods for obtaining deposited chalk, which were considered in the article. The most rational method seems to be the carbonation of calcium hydroxide with carbon dioxide. The implementation of this method is possible at commercial lime production plants, which will not only solve the important environmental problem of carbon dioxide emissions in such industries, but also will allow expanding the market for high-quality calcium carbonate, which is in demand by various industries.

Keywords: calcium carbonate, chemically precipitated chalk, lime, calcium oxide, calcium hydroxide, carbon dioxide, carbonation, commercial lime

The results of the analysis of quality parameters of building materials used for insulation of walls of residential buildings are presented. The problem of increased consumption of thermal energy for heating needs is identified, the solution of which is to increase the thermal characteristics of the enclosing walls of buildings by means of their insulation and protection by the system of a hinged ventilated facade.

Keywords: Hinged ventilated facade, thermal characteristics, influencing factors, energy efficiency

This article discusses the most common materials and how they are used to protect against ionizing radiation used for medical purposes. Comparison of technical and economic devices for the construction of a protective fence from the described radiation protection materials is presented. The effectiveness of the use of self-adhesive polymer radiation-shielding materials for protection against insulation with voltage up to 100 kV has been established.

Keywords: gamma radiation shielding, radiation shielding, EPDM, metal oxide, barite, polymer composites

The article discusses the possibility of increasing the physical and technical properties of the sands of the Usklyai field in the Republic of Mordovia from the technological modes of their enrichment. The prospect of their enrichment due to preliminary screening and washing with water is proved.

Keywords: building sand, cement concrete, mortar, particle size modulus