Innovations and Technologies in Construction

At the present time the development of new generation building composites, distinguished not only by high performance characteristics, but also contributing to the optimization of the system “human-material-living environment” is actual. In construction, sand-lime bricks are widely used as wall material. According to the normative documentation in its production pure quartz sand with a minimum content of clay impurities are used. However, there is a large proportion of quartz sands containing clay impurities. Such rocks do not satisfy the requirements of normative documents to sands for silicate materials. The urgent task is to conduct researches on development of building composites of new generation with the use of this type of raw materials. As a result of this research it is shown that fine sands characterized by the presence of clay impurities, represented by miscible clay minerals can be used as raw materials for the production of silicate materials. The use of such raw materials can optimize the microstructure and accelerate the synthesis of new formations represented by low-base calcium hydrosilicates. Increase of strength characteristics of products is caused by formation of new formations of increased degree of crystallinity, and also at the expense of optimization of granulometric composition. The content of the required percentage of used raw materials in the raw mix of sand-lime bricks contributes to an increase in strength characteristics of raw bricks by 2 times, the finished product by 1.8 times, which simplifies the production of products of complex shape.

The article represents a method for calculating the structural elements of surfacing on the working bodies of an impact-vortex mill. The method enables to calculate the geometric dimensions of the grid cell, taking into account the properties of the crushed materials and the method of applying to the working surface of the beater. It contributes to pressing the crushed material into the cell, and reduces the wear rate of the beater, due to the absence of full contact with the working surface. The dimensions of the cell are selected in such a way that the resulting pushing force is equal to or less than the holding force, but it remains sufficient for surfacing the impact-vortex mill beaters on the working surface. It is proved that the pressing and retention of crushed material particles in the cells is largely determined by its geometric dimensions, as well as the physical and mechanical characteristics of crushed rocks. The design of the beater is proposed, which increases its durability by reducing the contact area of the crushed material with its working surface.

A large amount of research and previously obtained experimental data allows us to conclude with a high degree of confidence that one of the key roles in the synthesis of alkali-activated binders, cement, concretes, etc. plays an alkaline component or activator, which, in fact, is the initiator of all structure-forming processes during the hardening of the system. In this study, we studied the features of the synthesis of alkali-activated binders with different component compositions using a complex of industrial waste “citrogypsum—electrometallurgical slag” as a solid-phase component. Based on the obtained experimental results, it was found that the addition of 10% citrogypsum promotes an increase in strength by 13% (from 4.9 to 5.54 MPa), i.e., a synergistic effect is observed. A similar trend: higher density values are provided with the combined action of the components (compaction up to 3–5%) versus similar values for the components that form a solid structure separately. The study of the effect of the type of alkaline activating agent showed that both activators used in the work (NaOH and Na2SiO3) do not have a significant effect on the strength indicators of synthesized alkaline-activated binders with citrogypsum. Moreover, the dosage of the introduced alkaline agent up to 5% reduces the compressive strength from 19% (for NaOH) to 43% (for Na2SiO3).

The study was aimed at evaluating the effectiveness of using polymer-colloidal complexes based on acrylic and styrene as well as traditional ionogenic surfactants based on silicone compounds to stabilize soils in the preparation of materials based on sandy, coarse clastic and technogenic soils for the construction of load-bearing and additional base layers of motor road pavement. It has been established that the use of polymer-colloidal complex based on acrylic acid butyl ester copolymer and styrene has high efficiency in the development of composite material from coarse clastic soils, while the use of stabilizing additives for soils does not provide a significant increase in the physical and mechanical characteristics of samples based on sandy, coarse clastic and technogenic (granulated asphalt concrete) mixtures in complex with cement. The results indicate that the particle size composition of the mineral part has a significant impact on the efficiency of the use of additives for various functional purposes. Polymeric styrene-acrylic dispersions have a more significant effect on the composite material with coarse-grained particle size composition (C-6). It is connected with a more complete polymerization of the film on the surface of internal pores of the composite, which affects the level of structure formation of the whole system. It has been established that the removal of water from polymeric dispersions leads to the formation of its supramolecular structure at the boundary of the mineral binder (cement) and stone material, which contributes, as a rule, to increasing the adhesive interaction between them.

The composition and level of outgassing of a protection material based on a polymer composite filled with amorphous boron at temperature and radiation exposure has been studied. An assessment of the danger of gas emissions under conditions of overheating of the material in an emergency situation is given. The sanitary-chemical characteristics of the protection material have been obtained. It has been established that the level of air pollution when the material is overheated to 180 °C for 1–2 days does not exceed the maximum allowable concentration of harmful substances in the air of the working area established for industrial premises. The specified temperature can be tolerated under conditions of overheating of the material in an emergency situation. As a result of overheating of the material in the temperature range of 190–200 °C, a sharp increase in gas emissions was found with an excess of the MPC level provided for by the toxicological and hygienic requirements for protection materials for class V premises. The overheating temperature of the material allowed in an emergency situation should not exceed 180 °C.

New requirements for the operational reliability of highways lead to the need for the expanded use of polymer-bitumen binders (PBB) in road construction. The traditional technology for the production of polymer-bitumen binder includes very energy-consuming processes: bitumen preparation, polymer grinding in a colloid mill and additional exposure in containers at temperatures above 170 °C. This leads to an increase in the consumption of electricity and fuel (most often it is natural gas or fuel oil) and, as a result, to an increase in the cost of the final product. In addition, the process of binder synthesis for a long time at high temperatures leads to increased aging, which significantly reduces the service life of this material in the pavement. The article presents the results of studies on the effect of polymer-bitumen concentrate (PBC) on the characteristics of bitumen. It has been established that the use of PBC in a bituminous binder leads to an increase in the temperature range of plasticity, elasticity, cohesive strength with a decrease in the viscosity of the modified bitumen and an increase in the softening temperature. Thus, the expediency of using a complex additive containing a polymer and surface-active substances (surfactants) that can be distributed in bitumen without the use of a colloid mill and a plasticizer has been proven to improve the quality of the organic binder. It is shown that the use of the PBC modifier can significantly reduce the energy intensity of the process and reduce emissions of volatile bitumen components.

We studied the change in the elastic-strength parameters of the Etal-247 epoxy resin polymer cured by the Etal-45 M hardener depending on the cyclic exposure level. It was established that the increased cyclic loading from 40 to 80% of the sample tensile strength (without cyclic loading) leads to the increased mechanical strength of samples at the failure stage by 12–23%. Cyclic exposure corresponding to the total loading of 96 mJ/m3 leads to the increased relative elongation under maximum load at the failure stage by 5–7%, and the elastic modulus increase of 12–18%. The relative polymer elongation at break in the initial state is 8.05%, decreasing to 5.74% with an increase in the cyclic stress. We offer an algorithm for estimating the effect of cyclic loads on the kinetics of failure accumulation in polymeric materials. We study the effect of the change in intensity and frequency of cyclic loading on the kinetics, and specific indicator of failure accumulation in Etal-247 epoxy resin samples cured by the Etal-45 M hardener. We found a decrease in specific index determined for the failure stage by 4–17% with an increase in the cyclic loading from 10 to 20 MPa compared with the same indicator obtained for the control series of samples without cyclic exposure.

Fire protection of building structures is an integral part of the system of measures to ensure fire safety and fire resistance of buildings and structures. The scope of various methods of fire protection is determined taking into account the required fire and technical characteristics of structures, the type of the protected structure, temperature and humidity conditions of operation and production of fire protection works, aesthetic and other requirements imposed on the structures. Fire protection is designed to increase the actual fire resistance of structures to the required values and to limit the spread of fire through them. This task is performed through the use of heat shields and heat-absorbing screens, special design solutions, flame retardant compositions, technological methods and operations, as well as the use of materials of reduced flammability. The paper presents the results of studies of flame retardant, physical and mechanical, weather-resistant properties of flame retardant foaming coatings. The most effective polymer film-forming catalysts, flame retardants, fillers are given. The selection of components of flame retardant foaming coatings is made. The optimum composition for a thermally resistant foam coating layer with the introduction of mineral fillers: wollastonite (up to 20–30%) and vermiculite (up to 10%) has been determined. Attention is paid to the possibility of reducing the flammability of coatings by physical and chemical methods. It is shown that in the process of shrinkage of the foaming coating layer under the influence of high temperatures, the needle fibers of wollastonite fusing create a barrier to burnout of the remaining part of the film formation. At the same time, as the specific gravity of perchlorvinyl resin increases from 1.0 to 1.4 g/cm3, the impact strength and adhesion increases. It has been proved, using the capacitance-ohmic method that the protective properties of coatings increase with the introduction of wollastonite and ammonium phosphate into the composition. As a result of studies, the possibility of partial replacement of expensive components of flame retardant materials, with a simultaneous increase in their weathering resistance and durability is shown.

The paper presents a methodology for evaluating the convergence of the results of composite part model calculations. The aim of the paper is to describe an algorithm for optimizing the strength calculations of the composite part structure by adjusting the parameters of the finite element mesh. The convergence is evaluated by sequentially varying the dimensions of the finite element mesh. The paper describes the difference of nonlinear calculation and its peculiarities relevant to the calculation of composite parts having surface contact of different materials. NX Nastran SolidEdge ST10 is used as the solver. Calculations of a composite specimen made of metal and metal-polymer were used to analyze the results. The parameters of the materials used in the calculations were used both from the built-in reference books and from the manufacturers’ data sheets. Among the analyzed calculation data, the parameters of safety margin, deformations and stresses were used. The results of the calculations have been systematized and presented in the form of appropriate graphs. The influence of the finite element mesh size on the accuracy of the results obtained and the expediency of using a finite element mesh with minimum dimensions are evaluated. The conclusion describes recommendations for the use of the proposed methodology for use by design engineers in the development of composite and other component designs in a nonlinear analysis.

The construction process is one of the main sources of consumption of a lot of raw materials which causes a huge amount of waste around the world. Finding reusable materials has become a challenge for many countries around the world. This paper presents a literature review that includes several experimental studies dealing with the behavior of reinforced columns using recycled aggregate concrete. Among the most important variables that have been focused on is the ratio of recycled aggregate concrete, centricity, and eccentricity of the applied loads, in addition to the behavior of columns using this type of concrete. Based on the results obtained from previous studies, it was shown that the comparison between normal reinforced concrete and recycled aggregate concrete showed a little difference in the performance and behavior, as concrete with recycled gravel has a structural performance that is slightly lower than normal reinforced concrete, which emphasizes the need to use concrete with recycled aggregate. Recycled in construction applications. In addition, the percentage of water content in concrete with recycled aggregates must be taken into account, as it is preferable that the water content must be enough in purpose of the saturation of aggregates well to provide a high resistance close to the resistance of natural concrete.

The paper presents data on the hydrophobization of the surface of powdered particles of zirconium hydride ZrH2 with polyethylhydrosiloxane. The surface morphology of ZrH2 particles was studied by scanning electron microscopy. The particle sizes range from 1 to 5 µm; there are nanoparticles up to 100 nm in size. The association of zirconium hydride particles into agglomerates is observed. Data on the granulometric composition of the ZrH2 powder are presented. According to the granulometric analysis, the transverse particle size of zirconium hydride does not exceed 31 µm, while most of the powder (80%) has a size not exceeding 10 µm. The specific surface of the particles is 25592 cm2/cm3, the modal particle diameter is 7.69 µm. Schemes are presented for modifying the surface of ZrH2 particles with ethylhydrosiloxane in a solution of a nonpolar solvent. The creation of a polyethylhydrosiloxane shell led to a significant increase in the wetting angle of the zirconium hydride surface from 71.5 ± 1.3° to 136.2 ± 1.6°. It was established that the modification of zirconium hydride led to a change in the hydrophilic surface to a hydrophobic.

Copper coating on the surface of titanium hydride shot was successfully obtained by quadrupole magnetron sputtering. The quadrupole magnetron system includes 4 rectangular magnetrons with an unbalanced closed magnetic system and a pulsed power supply. During the coating process, this system provides a significantly higher plasma homogeneity along the entire trajectory of the substrate products and the production of high-quality coatings with good adhesion. The microstructure of the copper coating was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It has been established that the thickness of the deposited coating is almost the same distributed over the entire surface of the shot and is ~986 nm. The interface between the deposited copper coating and titanium hydride shot can be traced over the entire survey area. The XRD results show that the copper coating deposited on the titanium hydride shot has a polycrystalline structure with a face-centered cubic lattice. The root mean square (RMS) surface roughness of the copper coating was ~3.67 nm.

The accumulation of residual stresses during the manufacturing process of a product can affect its performance in the future. Under the action of an inhomogeneous temperature field, polymeric materials can acquire indirect inhomogeneity, which is a change in physical and mechanical parameters (elastic and rheological), which are a strong function of temperature. The article provides information about definition of the stress–strain state of a polymer cylinder removed from an extruder. The heat exchange with the environment is taken into account, the temperature field is determined, and the change in stresses in the polymer body is studied, taking into account the development of creep deformations. It is shown that as a result of the development of stresses only from the inhomogeneity of the material caused by an uneven temperature field, the values of residual stresses in the body are very small and can be neglected.

The work is focused on assessing the effect of compatibility of polymer and various plasticizers on the properties and stability over time of the final product—polymer modified bitumen (PMB). To obtain the regularities of the influence of plasticizers on the stability of PMB at the initial stage of the research, the basic set of characteristics of the initial materials (bitumen and plasticizer) was determined. Control of structure formation of investigated binders was carried out by varying the concentration of plasticizer, which was used as: fuel oil M 200, oil I-50, “Uniplast”, the extract of selective oil purification (SPE), “Katgol”. For plasticizing additives such characteristics as: sample mass loss (volatility) in the range of technological temperatures of PMB preparation, aniline point indicator were investigated, as well as the group composition of plasticizing components was evaluated. In the course of the experiment the dynamics of changes of indicators of standard properties of modified binders was revealed, as well as their thermal stability (tendency to delamination and loss of weight during thermotreatment) due to the composition of plasticizer and its compatibility with the polymer used. It is suggested to investigate compatibility of components: plasticizer and polymer, at the preparatory stage, before preparation of laboratory PMB compositions. Recommendations on the use of plasticizers for obtaining effective compositions of polymer-bitumen binders have been developed. The contribution of polymer-plasticizer system compatibility on PMB resistance to destructive stratification and aging processes was studied. The importance of the raised topics for the industry is caused by the lack of a unified regulatory framework governing the requirements for plasticizers to modify bituminous binders, including the preparation of PMB. The conducted studies show that the compatibility of polymer and plasticizer has a key impact on the quality indicators of modified bituminous binders, but this aspect for the systems under consideration at the present time is not properly studied.

The new method for assessing the bearing capacity of structural elements of complex technical systems, taking into account single and complex factors in a wide range of durations (N = 103…108 cycles) with different amounts and combinations of their actions is proposed. Based on the system analysis, the classification of negative and positive impact factors was performed and it was shown that the main one of them, that reduces the bearing capacity, is a combination of corrosion and fatigue processes. As positive factors that increase the cyclic strength and durability of structural elements, the technologies for surface strengthening of welds and the application of new corrosion-resistant polymer coatings on stressed sections of elements are proposed. To assess the influence of the acting factors, 5 series of model tests were performed on the corrosion fatigue of steel samples with various combinations and numbers of factors (open air, corrosive environment, stress concentration, weld coatings, strengthening), which made it possible to form mathematical models of the action of these factors in the form of functions of corrosion coefficients for strength and durability. Unlike the current calculation method, which assess the bearing capacity only at the inflection point of the branches of the corrosion fatigue lines ( $${\rm N} \approx$$ 7 ⋅ 106 cycles), the new method makes it possible to evaluate the strength and durability in the entire range of $${\rm N}$$  = 103…108 cycles and, by clarifying the calculation procedures, to ensure high productivity and reliable uptime of specified elements with minimal material consumption.

The purpose of the conducted research was to optimize the foam fiber concrete technology and develop a methodology for selecting its composition based on the methods of mathematical planning of the experiment and analytical processing of its results. Processing and optimization of experimental data made it possible to establish the influence of variable factors on the properties of foam fiber concrete samples. It has been established that the fiber consumption has a significant effect on the strength and density of concrete, and the length of the basalt fiber affects only the strength of the samples. The graphical interpretation of the data obtained makes it possible to determine the consumption of basalt fiber depending on the required strength of the products and the consumption of Portland cement. The specific strength of foam fiber concrete is adopted as an optimization parameter. The research results can be used in the development of methods for selecting the composition of foam concrete reinforced with basalt fiber.

The paper considers the possibility of using the FT-IR spectroscopy method in the production of alkyd varnishes and resins to control various stages of synthesis. A number of samples were analyzed at different stages of synthesis, selected under production conditions at the stages of transesterification and polycondensation. The formulation of pentaphthalic resin is presented, the chemistry and features of obtaining alkyd resins are analyzed. Having considered the issues of express control of the production of alkyd varnishes, the possibility of controlling the studied stages by infrared spectra in the laboratory was investigated and analyzed. It has been established that the IR spectra of samples taken sequentially during the synthesis can be used to control the course of the chemical reaction of polycondensation in the technological process. Control can be carried out according to three main absorption bands, taking into account the identified patterns observed in the synthesis process: stretching vibrations—OH; C–H stretching vibrations of olefins (oils) and arenes (phthalates); valence antisymmetric and symmetric C–H methyl and methylene groups; bending vibrations of four aromatic ring hydrogens.

This paper presents studies of the surface of titanium hydride fraction samples modified by applying to its surface an organic silicon oligomer and boric acid chemically from aqueous solutions, using methods of optical and scanning electron probe microscopy. To determine the surface topography of a solid, we used high-resolution scanning probe (atomic force) microscopy using the MFP-3D Stand Alone (MFP-3D-SA) AFM microscope. The presence of hydroxyl OH-groups on the surface of the initial titanium hydride was established by infrared spectroscopy methods. A significant increase in the intensity of absorption bands at 3480 and 3490 cm−1 (OH-groups) was recorded. Activation of the titanium hydride fraction surface with an organic silicon oligomer significantly increased the concentration of hydroxyl OH-groups on the surface of vacuum-dried titanium hydride fraction at 100 ℃. We observed a difference in the surface structure of the initial and activated titanium hydride due to the formation of polysiloxane shell, as well as a difference in the surface structure of titanium hydride fraction containing polysiloxane and borosilicate shells due to the vitrification of boron oxide at 300 ℃. The surface of a modified titanium hydride fraction containing a borosilicate shell showing a 4.2 µm atomic force scanning microscope probe stroke relative to the OX axis, small reductions of characteristic probe dips and elevations with height and depression differences to up 10 nm throughout the scanning area are visible.

Gypsum-containing wastes are a promising source of raw materials for the production of gypsum binders. However, they have specific features that require the development of alternative approaches and technological regimes in order to ensure the high quality of the final product. The purpose of the article was to study the influence of moisture content of gypsum-bearing waste and firing temperature on the specific surface of the gypsum binder, as well as the compressive strength and average density of gypsum paste based on it. The gypsum-bearing material was citrogypsum. It is a waste product of the biochemical synthesis of citric acid. The experiment was carried out using the method of mathematical planning. Burning of citrogypsum was carried out in a laboratory oven according to a given temperature regime. Using the statistical computer processing of experimental data, regression equations were obtained; graphic dependence as nomograms are constructed; the influence of variable factors on the controlled parameters was assessed. It has been established that the optimal, from the standpoint of energy consumption, is the binder burning at a temperature of 150 ℃ and the lowest possible raw material moisture content of 5%. Increasing the burning temperature above 150 ℃ is not economically workable and adversely affects the compressive strength of the gypsum stone, as well.

Corrosion of steel reinforcement is the main cause of failure of concrete structures. The most effective way to prevent degradation of concrete structures is to replace the steel with a corrosion-resistant reinforcing material, such as a fiber-reinforced composite. The types of composites that are best suited for reinforcing concrete provide high strength, stiffness, and compatibility with concrete. They are rod-shaped elements, molded and processed in such a way that the surface texture and irregularities provide mechanical adhesion to concrete. The authors considered the types of rods made of fiber-reinforced composite, such as fiberglass, carbon fiber, basalt-reinforced plastic and aramidoclast, in comparison with steel as a reinforcement material. The reduced resistance to heat transfer of an inhomogeneous part of the structure is determined taking into account linear and point thermal inhomogeneities using the example of a coating slab with a reinforced frame. Based on this calculation, it was found that the least energy efficient model is a plate reinforced with steel reinforcement, in which additional specific linear heat losses are 14.5 times lower than the rods made of fiber-reinforced composite, the reduced heat transfer resistance is 10%, the heat transfer resistance of a homogeneous part of the structure is 13%.

A layer of aluminum oxide on the surface of a highly filled polymer composite based on polyimide and tungsten oxide was obtained by the method of detonation spraying. The thickness of the resulting coating is from 80 to 120 μm. The X-ray diffraction pattern of the coating showed the presence of only one modification of aluminum oxide—α-Al2O3. The erosion resistance of coated and uncoated polymer composite specimens at 25 °C was studied in accordance with ASTM G76-02. The test time for all samples was 1 h, the abrasive material consumption was 2.2 g/min, and corundum powder (Al2O3) with an average fraction of 50 μm was used as the abrasive material. The air pressure was 0.35 bar. The impact of the abrasive material jet was carried out at angles of 30, 60, and 90°. It has been established that the erosion wear of specimens with a ceramic coating of α-Al2O3 is almost an order of magnitude lower than that of specimens without a coating.

The aim of this work is to study the durability in biological media of cement composites based on biocidal cements. Formulation of biocidal cements was carried out using the following components: Portland cement clinker (JSC “Mordovcement”, Russia); calcium sulfate dihydrate (Poretskoe deposit, Nizhny Novgorod region); fly ash of Krasnoyarsk CHP-3 (Russia), biocide preparations: sulfuric acid sodium, sodium fluoride. The finished specimens were incubated in a medium consisting of 10 species of mycelial fungi. Identification of dominant micromycetes infesting the surface of composites made on ordinary Portland cement and several types of biocidal cements obtained using different biocidal preparations was carried out. No more than 2 species of mycelial fungi were found around specimens based on biocidal cements as opposed to ordinary ones—against 7–8. At the same time, it is important that the absence of the most dangerous for human health micromycetes (Aspergillusniger) around the composites made with biocidal cements was revealed. Long-term tests (up to 180 days) revealed high fungal resistance and fungicidity of individual compositions with biocidal additives and insignificant variability of properties both in standard biological environment and in the products of their metabolism. The biocidal properties of the developed composites were tested in full-scale climate conditions of the Black Sea coast and the Leningrad Region. Developed biocidal cements with active mineral additives are recommended for use in buildings with biologically active media in the manufacture of concrete and other cement composites with increased biological resistance.

The paper deals with the main construction materials used in the construction, repair and reconstruction of buildings and structures, which include gypsum, lime, and clinker. Obtaining building materials is associated with technological processes, grinding is the most energy-intensive of them. Grinding of construction materials is carried out in ball-tube mills, the design of which is constantly being improved. The new design of the ball-tube mill is equipped with an inclined partition. The grinding bodies in the new scheme of the ball-tube mill, unlike conventional designs, move not only in the cross section of the crushing cylinder, but also in the longitudinal direction, which significantly affects the kinetics of motion. The fundamental differences in the kinematics of motion, velocity and energy modes of grinding bodies during the cycle compared to conventional ball-tube mills are considered. The calculation diagrams and graphical results of calculations are given: the coordinates, velocities and inertia of the ball at the moment of its collision with the mill crushing cylinder and the energy value of the ball under the conditions of its cross-longitudinal motion. The characteristic sections of the phases of motion of grinding bodies during the full cycle of rotation of the crushing cylinder and the behavior of grinding bodies in each of the sections is considered. The most effective zones of the work of grinding bodies are indicated. A comprehensive analysis of the loading operation is given. The main difference between the kinetics of motion of grinding bodies in a mill with an inclined chamber partition from conventional ball-tube mills, consisting in different values of the angle of incidence, velocity and energy of the ball at the same angle of separation, is considered. The generalizing conclusions of the energy and speed parameters of the ball-tube mill in the grinding of construction materials are made.

The design, construction, and operation of high earth dams located in seismically active zones of the Republic Uzbekistan require constant improvement of the computational methods for their calculation to predict the loss of strength (formation of cracks, loss of slope stability, etc.). In the current normative method to calculate hydro-technical structures for seismic effects, a cantilever rod is considered; this method does not allow taking into account the non-one-dimensional nature of the oscillation and the real physical and mechanical characteristics of soil of the structure and foundation. The assessment of the dynamic stress–strain state of high earth dams under seismic action within the wave theory is the most difficult problem in mechanics. This article presents a mathematical formulation for the numerical solution of a non-stationary problem for an earth dam with a foundation in a plane elastic statement. The problem of studying the stress state of the high Charvak earth dam under shear dynamic impact on the foundation (in the form of a seismogram) was solved by the numerical method of finite differences. So-called radiation conditions were set at the boundaries of the studied finite domain of the foundation. The solution is represented as a distribution of lines of equal displacements, stresses over the dam body depending on time. At that, the most vulnerable zones of the considered earth dam were identified.

The paper presents the results of blast furnace slag treatment by low-temperature non-equilibrium plasma method. The blast furnace slag treatment process is carried out at the Moscow State University of Civil Engineering laboratory. An alternating current generator with voltages up to 8000 V and frequencies up to 40 kHz between the electrodes creates a low-temperature unbalanced plasma region. Research results show that, after blast furnace slag is treated by low-temperature non-equilibrium plasma method, cracks appear on the blast furnace slag surface. This leads to a decrease in grain size and an increase in the blast furnace slag Blaine fineness. In addition, the research results also show that the compressive and flexural strengths of the mortar sample using plasma-treated blast furnace slag are 71.08 MPa and 10.42 MPa, respectivel. That is higher than the mortar sample using the blast furnace slag untreated plasma, respectively 0.05 MPa and 8.70 MPa.

In surface engineering technology, coatings have attracted widespread attention due to their ability to impart excellent tribological and anti-corrosion properties to the surface of materials. However, to improve the protective and functional properties of coatings, a more complex combination of elemental composition is largely assumed. In the present work, the mechanical, tribological, and anticorrosive properties of a Ni–B–Cr–C composite coating deposited by DC magnetron sputtering on a Ni–Cr–B4C composite target are investigated. The composite film showed good mechanical properties with a hardness of 10 GPa and an elastic modulus of 271 GPa. Wear tests carried out with a ball-on-disk tribometer showed that the Ni–B–Cr–C coating had good wear resistance. The mechanical wear of the composite coating is dominated by abrasive, oxidative and adhesive wear in the atmospheric environment. The coefficient of friction of the composite coating is in the range from 0.84 to 1.01. It has been established that the Ni–B–Cr–C composite coating increases the corrosion resistance of the steel substrate.

A fundamental factor in the proportioning of stable bitumen emulsions from a blending point of view is the choice of emulsifier and its effective concentration in the aqueous phase composition. The purpose of the work was to establish a correlation between the properties of the aqueous phase with different emulsifier content and the stability of the resulting bitumen emulsion. The indicators of surface tension of the systems and the wetting angle were taken as the criteria for evaluating the effectiveness and optimality of the emulsifier concentration in the aqueous phase. Research shows, that wetting efficiency of the aqueous phase, depending on the emulsifier concentration, correlates with the surface tension of the respective solutions. The greatest stability factor of the systems is characterized in samples of bitumen emulsions prepared in aqueous phases, previously noted as effective. The aggregative stability of bitumen emulsions is primarily associated with the flocculation and coalescence processes in the system, it is obvious that effective water-emulsifier solutions prevent these processes from initiation, maintaining the structure of the emulsions stable.

In radiation materials science, the issue of surface modification in order to improve the operational properties of materials is relevant. This manuscript describes an electrochemical method for obtaining co-deposited (alloyed) coatings from copper reinforced with nanodisperse particles of tungsten carbide, which contains carbon of the frame structure. Spherical granules of titanium hydride were used as a substrate. The advantages of this method are presented. The results of scanning electron microscopy of the obtained alloyed coatings are presented. Electrochemical co-deposition of copper and nanodispersed particles of tungsten carbide provided a simple and effective coating on the surface of spherical granules of titanium hydride, with a thickness of about 50 μm. Obtaining an alloyed coating on pre-chemically modified titanium hydride granules contributes to obtaining a strong adhesive contact at the boundary between the surface of the titanium hydride sphere—an aggregate-like microrelief of hydroxytanyl—and a tungsten carbide-hardened copper shell, by increasing the contact area. This simple and effective electrochemical modification of the surface can be additionally used for various products or their individual parts. In addition to copper, nickel, cadmium, chromium or some alloys can be used as metal elements deposited by electrolytic means.

This article reveals the results of the conducted research on the production of ceramic products of light shades based on red-burning clay raw materials of the Doroganovskoye deposit. Based on the analysis of literary sources, it was found that the most common way to lighten a ceramic shard is the introduction of dispersed chalk into the mass. During the research, chalk was introduced into the composition of the mass in an amount of 10–30%. However, this led to a decrease in strength and an increase in water absorption in burnt products. In order to obtain light-colored ceramic products with high physical and mechanical properties, a modifying additive was additionally introduced into the composition of the masses, in addition to chalk. It was determined that this additive makes it possible to intensify the firing processes and makes it possible to obtain light-colored samples with a lower content of carbonate-containing material in the charge. X-ray phase studies have established that the mineralizing effect of this additive occurs due to its sufficiently low melting point. Due to this, the dark-colored mineral hematite is involved in the formation of new minerals characterized by low-intensity coloring, which ensures the production of light yellow samples. In addition, an increased content of anorthite and helenite is formed in the shard, which leads to an increase in the strength of the samples. Thus, laboratory studies have shown that it is possible to obtain light-colored ceramic products from the red-burning clay raw materials of the Doroganovskoye deposit by semi-dry pressing. The optimal composition of the ceramic mass and the production parameters for this are as follows: the amount of chalk in the mass should be 20%, the content of the mineralizing additive should be 1%, the preparation of the press powder should be carried out with preliminary plastic processing of the mass, the specific pressure of pressing samples is 20 MPa, the firing temperature is 1000 °C. This will make it possible to obtain burnt samples of light yellow color with a compressive strength of 36.1 MPa and a water absorption of 14.6%.

The reliability of reinforced concrete structure by external reinforcement with composite materials is ensured by the joint work of the reinforcement element and the main reinforced structure. The current standards do not contain provisions for the experimental evaluation of the adhesion of external composite reinforcement with concrete. The provisions on the design of reinforcement of reinforced concrete structures with external composite reinforcement do not take into account shear deformations in the contact seam, adhesion of composite material with concrete it is indirectly estimated by the introduction of the coefficient of the working conditions of the composite material when assigning its design resistance. A method of experimental evaluation of the adhesion of external composite non-metallic reinforcement with concrete is proposed, the patterns of deformation of composite reinforcement elements are revealed, the nature of the destruction of the adhesive joint of the adhesive joint of the composite material with concrete is established.

This article discusses perspective directions of development of pneumatic mixers for mixing dry building mixes. Pneumatic mixers are modern equipment used for mixing dry building materials and fine materials that meet the requirements for environmental and industrial standards that surpass mechanical mixing units in their technical characteristics and do not harm the health of operators. Mixing materials with high-intensity movement of particles through the mixing chamber and with other material particles allows for obtaining a finished mixture with a high percentage of uniformity, which allows increasing the quality characteristics of the finished product, which is of no small importance in the manufacture of building materials. In this article, we present a new patented design of a pneumatic mixer, the distinctive quality of which it improves the properties of the final product and high uniformity of the finished mixture due to intensification of the mixing process. The method for calculating the process of mixing the components of bulk material in a pneumatic mixer is provided. According to the results which we obtained, the ratio that determines the change in the concentration of a selected component of bulk materials in the cylindrical volume of the mixing chamber. The results of this article can be used in the design of pneumatic mixers for mixing dry building mixtures.

The article presents a method for determining critical loads for centrally compressed wooden bars with a cross-sectional stiffness variable along the length. Rectangular cross-section bars are considered, the section height of which varies according to a linear law, and the width is constant. The solution is carried out in the elastic formulation. To obtain a solution that is valid for an arbitrary bar geometry, dimensionless parameters are introduced. When solving the stability problem, the basis is the static Euler criterion. The solution of the main resolving equation is performed numerically by the finite difference method. As a result, the task is reduced to the problem of matrix eigenvalues. The implementation of the calculation is performed in the MATLAB environment. Comparisons are made with the current Russian standards for the design of wooden structures. In Russian design standards, a controversial provision is that the variable stiffness of the bars is estimated by the same calculation formula, regardless of the type of fastening. It has been established that the error of Russian design codes for a bar hinged at the ends can in some cases exceed 5%. Corrected calculation formulas suitable for engineering calculations are proposed. In addition, to confirm the reliability of the results, a finite element analysis is performed in the LIRA-SAPR software package.

Polymer composites with radiation protection fillers play an important role in the space and nuclear industry. Along with radiation resistance, the multifunctionality of the polymer composite is also required to meet the needs of industry. The introduction of hybrid fillers into a polymer matrix can have a beneficial effect on protective properties, but also on the multifunctionality of polymer composites. This article examines the influence of the distribution of a hybrid filler in a polytetraforoethylene (PTFE) matrix on the microstructure and hardness of the composite. Tungsten carbide, boron carbide, bismuth oxide and titanium hydride—four types of filler with different average particles from submicron to the micron. The homogenization of the mixture was carried out in a jet-type mill. The molding of the polymer composite was carried out by hot pressing. It was established that the hybrid filler is evenly distributed by the PTFE matrix. The interfacial border between the matrix and the particles of the filler is very dense. It is shown that the maintenance of a hybrid filler into the PTFE matrix significantly increases the hardness of the polymer composite.

In this work, by numerical simulation using the Abaqus software package, the stress–strain state of a bent reinforced concrete element of a rectangular cross section is investigated. Numerical modeling of the element is performed by volumetric finite elements, taking into account the non-linear (actual) state diagram of concrete, described by the model of plastic fracture of concrete with damage (CDP). Reinforcement is specified by rod finite elements, with a combination of elastic properties and metal plasticity model. The loading of the beam element in the model is performed statically with the application of concentrated forces at the centers of the thirds of the design span. As a result of the finite element calculation, the distribution of stresses in concrete and reinforcement according to Mises, deformations of finite elements along the main axes, as well as a model of concrete damage with increasing load were obtained. The results obtained showed a high convergence with the experimental data of testing beams for bending along a normal section, which allows using this algorithm for automated finite element analysis in the design of bending reinforced concrete structures.

In order to expand the raw materials base of building materials industry, not only industrial waste, but the off-grade natural aluminosilicate raw materials—clay minerals of incomplete mineral-forming stages,—have been more and more involved into the industrial usage. As initial materials the steelmaking slag with basicity factor 1.15 and characterized as neutral and the clay-containing component—sandy loam—were used in this study. The paper presents the results of dry milling and MW (microwave) treatment of sandy loam influence on strength properties of clay-slag autoclaved silicate concretes. It has been demonstrated that dry milling of sandy loam provides the highest gain of specific surface—26.15%, while using the MW-field (power 800 W, 2 min.) increases the specific surface by only 8.83% in comparison with the original sample. Then the reactive properties of mechanically activated sandy loam are considered. The reactive properties of sandy loam, modified with microwave radiation, are composed of the increased sorption capacity to Ca(OH)2 of the dispersed clay minerals and reactive polymorphic modifications of quartz. At the optimal ratio, wt%, clay component: slag = 40:60 the highest strength properties were obtained at using the sandy loam, activated in the microwave field at the following radiation parameters—power 800 W, treatment time 2 min. The gain of strength properties made up 60% as compared to the non-activated sandy loam.

Bentonite is a clay obtained from volcanic rock. It is a type of smectite clay containing the mineral montmorillonite and a certain amount of quartz, feldspar, cristobalite, pyrite, illite, and mica. Montmorillonite is classified as a 2:1 clay mineral because it consists of two silicon tetrahedral sheets that share oxygen atoms with an octahedral aluminum sheet sandwiched between them. The authors studied the issue of using bentonite as an additive in gypsum plaster and putty mortars. The ability of bentonite to swell can be used to optimize the microstructure of threshold gypsum, increase the proportion of small pores, improve its thermal insulation and vapor permeability. A chemical and phase analysis of the composition of semi-aqueous gypsum and bentonite was carried out. At a ratio of bentonite/water of 1:5, unlike other ratios, there is no residual water on the surface of the mixture, bentonite is completely saturated with moisture. It is expedient to use such a ratio in further research to obtain a finely porous structure of threshold gypsum.

The construction site geotechnical conditions are an important factor in the structures seismic resistance estimation. Based on the earthquakes consequences analysis to buildings with the same structural schemes and overall dimensions, the construction site estimated seismicity dependence on the base soil seismic stiffness and the transverse waves speed is fixed in the seismic building design code. In the research, a math modeling experiments for completely identical structures, but with different foundations types on identical soil conditions, were performed. The performed calculations analysis showed a significant discrepancy in the structures response under seismic impact for different foundations types.

It is known that the failure of quasi-brittle materials such as wood is accompanied by an accumulation of damage and a decrease in the effective cross-sectional area of the specimen. At a certain stage of loading the process of damage accumulation significantly accelerates and is characterized as a catastrophic process. Purpose of work: developing a model of catastrophic stage of damage accumulation under uniaxial compression of wood. Damage accumulation is characterized by a damage function. The choice of the damage function is not the only one. Two such sigmoid functions are discussed. Only one of the two functions provided the ability to quantify the rate and acceleration of catastrophic damage accumulation. It is shown that the rate of damage accumulation increases with increasing axial strain and reaches an extremum in the middle of the theoretical process duration. The theoretical dependence is not fully realized, since the failure occurs in the vicinity of the point of rate extremum, but does not reach it. Analytical and graphical estimates of the rate and acceleration of damage accumulation were obtained. The simulation results are in agreement with the data known from the literature.

The responsible heavily loaded structural elements (butt welds and sections of their location) of the complex technical systems, which are mainly operated outdoors, are impacted by atmospheric influences and cyclic stresses, which are caused by load fluctuations, nature vibration processes, ambient temperature and changing weather conditions. These factors cause the appearance and development of corrosion-fatigue damage and can lead to cracking and fatigue destruction of structural elements. The factors affecting on the bearing capacity of structural elements, which are occurred in a complex form, in different amounts and combinations, are classified. The surface strengthening of the junction outside surfaces and usage of anticorrosive protective plating on them are selected from a number factors. So that, to magnify fatigue strength and durability is suggested to use a strengthening technology-surface plastic deformation of welds. The physical and mechanical phenomena of the appearance and development of corrosion-fatigue processes are considered and ways to enlarge the strength and durability of elements using new corrosion-protective polymer platings (Belzona 1111) in the location of butt welded junctions are outlined. A series of techniques, e.g., static tests of steel samples with and without platings in a corrosive solution was performed and its effectiveness for application in the critical nodes was confirmed. The effectiveness of the implementation of these, process operations which enlarge the bearing capacity of the complex technical system, has been proven.

The article deals with the production of construction materials and products based on them, the main ones of which are cement, concrete, brick, stone, lime. The source for obtaining construction materials is natural resources that are subjected to various technological processes: grinding, classification, dosing, mixing, molding, heat treatment. The most energy-intensive process is grinding. The main equipment for grinding construction materials are ball-tube mills, which are actively used in industry and are constantly being improved. The main issue of improvement is to reduce the power consumption of a ball-tube mill with cross-longitudinal movement of the load. A comparative analysis and the possibility of using the known methods for calculating the power consumption of the drive of a ball-tube mill with cross-longitudinal movement of grinding bodies is given. The calculation scheme of the ball-tube mill, equipped with an inclined partition, is considered, and a detailed analysis of the mode of motion of the grinding bodies is described and given. Conclusions were obtained about the change in the value of power consumption of the ball-tube mill drive from minimum to maximum, due to the change in the level of the grinding bodies in both chambers of the mill during the cycle from maximum to minimum. Generalizing conclusions were made and it was proposed to reduce the mass of grinding bodies in proportion to the value of additional power consumption, in order to reduce the amplitude of the torque fluctuation on the shaft of the crushing cylinder.

Today a significant number of buildings and structures, which have already exhausted their resource, require inspection and diagnostics that aims to assess the technical condition, as well as making decisions on the possibility of their further operation, the need for overhaul, reconstruction, etc. When examining the construction of buildings and structures and assessing their technical condition it is not always possible to obtain complete statistical information about the monitored parameters, and there may be a situation in which complete statistical information may be obtained for part of the monitored parameters that allows to identify the distribution law and parameters of this distribution, and for another part of the parameters—incomplete. In such cases, when carrying out reliability calculations of a structure, the use of probabilistic-statistical methods can lead to inaccurate results and become incorrect. The combination of random and fuzzy variables in such situations when carrying out reliability calculations of building structures allows a more complete use of all statistical information obtained as a result of the survey of structures. The paper proposes a particular methodology for calculating the reliability of a beam with a corrugated wall by the criterion of compressed chord bending in the plane of the wall.

This article is devoted to the study of the intensifying ability of mineralizers in the production of white cement. Dried raw sludge was used as the initial raw mixture Limited Liability Company «Holcim (Rus) Construction Materials». The reagents CaF2 and NaF of “pure” qualification were used as mineralizers. The intensifying ability of mineralizers of calcium fluoride and sodium fluoride was studied under conditions of circulation and accumulation of alkali metal salts, depending on the input method. To simulate the circulation and accumulation of alkali metal salts, the reagent Na2CO3 of “pure” qualification was introduced into the raw sludge in the amount of 3.5 wt% Na2O on clinker. Calcium fluoride was introduced in the amount of 1.5 wt% CaF2, and sodium fluoride in the amount of 1.615 wt% NaF on clinker. Traditional (in the initial mixture) and separate input of mineralizers were used. It has been found that the circulation and accumulation of alkali metal salts lead to a decrease in the whiteness of the clinker. With the traditional input, the efficiency of the mineralizer at 1400 °C is low. The traditional input of mineralizers has practically no effect on the whiteness of the clinker at 1400 °C. Separate input makes it possible to increase the efficiency of the action of mineralizers and achieve a comparable degree of assimilation of free calcium oxide in similar samples even at 1300–1350 °C. Separate input has a positive effect on the whiteness of the clinker. The greatest efficiency was shown by separate injection of calcium fluoride under conditions of circulation and accumulation of alkali metal salts.

With the constant development of the cement industry, the requirements for quality indicators of the produced Portland cement are being tightened, which creates some difficulties in cement production. But at the same time, these requirements have a positive impact on the construction industry. One of such indicators of quality is the water separation of cements. It is believed that the process of water separation is influenced by many factors, such as: the presence of active mineral additives, surface-active substances, the specific surface of cement, the chemical activity of tricalcium aluminate, clinker and the type of gypsum. In the construction industry, there is a practice of using electricity to heat concrete during the winter period of concrete work. In this case, both reduced (down to 100 V) and increased (up to 400 V) voltages are used. Also, the main effect leading to an increase in the strength of concrete is hardening at elevated temperatures. The process of water separation is strongly influenced by the sedimentation stability of the cement slurry. And the sedimentation stability is affected by the ζ-potential of the particles. By itself, the ζ-potential has an electrical nature, so it must be influenced by an electric current. This fact should lead to a change in water separation. However, the effect of low voltage electric current on the processes of hydration and water separation has not been studied. Therefore, the purpose of the scientific work is to study the effect of an electric current with a voltage of 1.5 V on the process of water separation of cements. In this work, the effect of an electric current of 1.5 V on the water separation of cements from various manufacturers was studied using 5 different arrangements of positive and negative electrodes in a cylinder with cement mortar. A salt battery (manganese-zinc) was selected as a power source. It has been established that a low-voltage direct electric current equal to 1.5 V affects the process of water separation. The greatest impact was made on factory cements CJSC «Maltsovsky Portland cement» CEM I 42.5N and CJSC «Oskolcement» CEM I 42.5N. For cement CJSC «Maltsovsky Portland cement» CEM I 42.5N, a direct electric current with a voltage of 1.5 V reduces water separation by 86%, and for CJSC «Oskolcement» CEM I 42.5N water separation increases by 327%.

We studied the change in elastic-strength parameters of polymers based on epoxy resin Etal-247 and hardeners Etal-45M, Etal-1472, Etal-45TZ2 depending on the intensity of the cyclic tensile load (soft loading mode). The cycling levels were 40, 60 and 80% of the sample tensile strength without pre-cycling. We found that the tensile strength and relative elongation after cycling and subsequent stage of destruction for all levels of cyclic exposure vary in fairly narrow ranges. We revealed that for samples after pre-cycling, the strength characteristics are slightly higher compared to similar indicators without cyclic exposure, which is typical for cyclically hardening materials. We offer an algorithm for estimating the effect of cyclic loads on the kinetics of failure accumulation in polymeric materials. We studied the effect of cyclic loading level on the kinetics and the specific index of failure accumulation in samples of epoxy polymers. It is shown that a decrease in the level of tensile cyclic stresses from 80 to 40% with a simultaneous increase in the number of loading cycles (to achieve one level of loading) leads to an in-creased total failure rate, by 1.4–1.9 times on average. Stability of the specific index recorded at the stage of breaking and significantly lower values of the total number of accumulated failures of the Etal-247/Etal-1472 composition indicate the greatest prospects for the use of this polymer subjected to cyclic loads.

Due to a complex chemical composition and microstructure of many functional materials the problem of optimizing their parameters for applied purposes is associated with determining of charge carrier transport mechanisms. To modify the properties of CaSO4 ⋅ 0.5H2O we prepared composite samples: (CaSO4 ⋅ 0.5H2O)0.95–(FeSO4 ⋅ 7H2O)0.05 and (CaSO4 ⋅ 0.5H2O)0.90–(FeSO4 ⋅ 7H2O)0.10. In a dry atmosphere all studied samples also had a specific conductivity of about 10–9 S cm–1. It has been established that with an increase in relative humidity (RH) of the environment the specific conductivity increases according to a power law up to 10–7 S cm–1. The measurements were carrying out at a constant temperature of 28 °C and RH range of 35–90%. To study a proton conductivity of studied compounds a method of impedance spectroscopy was using. Conductivity was measuring in the frequency range 20 Hz–5 MHz. In (CaSO4 ⋅ 0.5H2O)0.95–(FeSO4 ⋅ 7H2O)0.05 samples and (CaSO4 ⋅ 0.5H2O)0.90–(FeSO4 ⋅ 7H2O)0.10 at above 40% RH granular conductivity was observed, an additional linear section was observed in (CaSO4 ⋅ 0.5H2O)0.90–(FeSO4 ⋅ 7H2O)0.10 samples which is responsible for the conductivity along grain boundaries.

The article presents the results of experimental studies of shear deformation on the process of grinding materials. The following values are taken as the investigated values: molding pressure, the angle of force exertion, the value of the weighted average size of the crushed particles and the pressing layer. As a result of mathematical planning of the experiment, regression equations were obtained and graphical dependences of the influence of the studied factors on the degree of material grinding and their final density were constructed. Organogenic limestone and clinker with an isotropic texture are the studied materials. The conducted studies allowed us to find out the range of rational values of the pressure value when grinding materials with different textures and physico-mechanical properties. The range within the limits for organogenic limestone is P = 75–150 MPa, and for clinker P = 150–225 MPa. The magnitude of shear deformations affects the degree of grinding. It is established that with an increase in the angle of application of force and shear deformations up to 45°, the degree of grinding of the studied materials increases.

The water resistance of autoclaved silicate materials can change in a wide range. The strength of calcium-silicate brick in the water can decrease up to 30%, which is explained by its high open porosity and possible content of some free hydrated lime, which on contact with water after some time passes into its soluble state, forming pores and cavities. The most water-resistant are dense silicate concretes, the cementing bond of which consists of hydrosilicates CSH (B), tobermorite, xonotlite. The paper considers clay-slag autoclaved composite materials, obtained with the use of steelmaking slaking slags and polymineral clay, of the following composition, wt%: slag—60; clay—40; lime—5, over 100%. As a water-repelling admixture the usage of oil-extracting industry waste kieselguhr sludge, generated at winterization stage of oil refining during oil clarification from waxes and wax-like impurities, was considered. Kieselguhr sludge contains 65% of organic matter, including 3.8% of vegetable waxes and wax-like substances, which provides it with hydrophobic properties. The findings have demonstrated that the optimal sludge content makes up 0.8% of solid components weight, which provides consistent strength and reduces water sorption and capillary suction of clay-slag autoclaved composite concrete samples almost by half in comparison with control samples of concrete without the additive. The operating principle of the sludge consists in leaching of amorphous silica, contained in diatomite, and its participation in low-basic hydrated calcium silicates synthesis in autoclaving conditions with the subsequent impregnation of the silicate matrix with the released hydrophobic components of sludge, which contain, among other substances, vegetable waxes and wax-like components.

The ability of some soil grains to move relative to others makes them look like liquids. At the same time, each particle of a granular medium, taken separately, has all the properties of a solid body. These particles form a granular body capable of absorbing external compressive loads, which makes granular bodies look like solids. In the article, considering soils as a dispersed, discretely isotropic medium (granular system), theoretically, by modeling the contact of soil particles with a solid smooth surface, the area of actual contact at various levels of convergence is established. At the same time, reference curves for the contact of various sands were established using their relative magnitude. For five types of sands, contact characteristics were determined depending on their density. For clay, loam and sandy loam, the dependence of the relative actual contact area on the plasticity number is determined. At the same time, in the range 0.25 ≤ Ip ≤ 0.75, analytical dependences for sandy loam, loam and clay of the relative actual contact density on the plasticity number Ip were determined.

The article is devoted to columns with local prestressing of tensile reinforcement. Such columns can be used with large eccentricities of the longitudinal force, for example, in industrial buildings. Prestressing of the reinforcement in the structures under consideration is created using tension couplings. The design of columns with local prestressing is described. The derivation of resolving equations for determining the stress–strain state at the manufacturing stage is given, taking into account the nonlinear properties of concrete. The calculation model is based on the hypothesis of plane sections. The problem is reduced to a system of two equations for axial deformation and element curvature. An algorithm for the numerical solution of the resulting system is described, which is implemented in the Matlab environment. A formula for the deflection of the element at the manufacturing stage is obtained. Verification was performed by comparison with the finite element software package LIRA in three-dimensional nonlinear formulation.

One of the most important advantages of polyurethane foams is the ability to produce products in one step. Foaming and curing of this insulation does not require heat supply due to the exothermic synthesis reaction that occurs when two or more liquid components are mixed, with simultaneous adhesion of polyurethane foam to various surfaces due to good adhesion to almost any materials. At the same time, having a low density, this foam polymer is able to withstand fairly large loads. Samples were taken from the tailings filtration field of the Stoilensky GOK (Gubkin, Russia) from various sites as the studied raw materials, their granulometric and chemical compositions were determined, and the harmonic diameters of the filler particles were determined. Based on the calculation results, the dependence of the foaming coefficient on the average harmonic diameter of the filler was determined. An experiment planning matrix has been developed, based on the results of which mathematical models of the dependence of the coefficient of foaming of laboratory samples of polyurethane foam filled with tailings were built. Three zones of tailings are considered based on the results of sampling. Analyzing the results obtained, a quantitative and qualitative assessment of the influence of each factor separately, as well as their combination, on the change in the “composition–properties” system was derived.