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EXAMINATION OF THE QUALITY OF NANOMATERIALS IN THE DEVELOPMENT AND APPLICATION OF CIRCULATING RESOURCES IN CONSTRUCTION

https://doi.org/10.34031/2618-7183-2021-4-6-48-68
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 48-68 p.
Abstract
The advantage of the equality indicator is the relative simplicity of definition and the possibility of periodic monitoring. According to the equality indicator, it is possible to assign repairs and predict the service life, assess the condition of the road surface. Experimental studies have proved that there is a connection be-tween the evenness of the coating and the strength of the pavement, which opens up the possibility of determining the structural strength of non-rigid pavement, which provides a given evenness of the coating for the last year of operation before major repairs. The question of assessing the impact of the unevenness of the road surface on the processes of development and accumulation of deformations, changes in the evenness of the coating during operation remain largely open. This is due to the multifactorial nature of the problem of predicting the equality of coverage, so it is advisable to use approaches based on direct measurement methods. Most of the existing models of interaction of a pneumatic or rigid wheel with a coating are designed for problems of pavement mechanics or car theory, therefore they cannot be unambiguously applied to determine the value of the dynamism coefficient. A significant disadvantage of these solutions is insufficient consideration of the deformative properties (modulus of elasticity) of the pavement.
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THE INFLUENCE OF FORCED CARBONIZATION ON THE PROPERTIES OF GYPSUM-LIME SYSTEMS BASED ON SECONDARY RAW MATERIALS

https://doi.org/10.34031/2618-7183-2021-4-6-69-81
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 69-81 p.
Abstract
The use of secondary raw materials for the production of building materials is a modern trend in solving environmental problems. In the Republic of Crimea, dumps of secondary raw materials – phosphogypsum and lime dust – have accumulated in large quantities at various enterprises. The analysis of phosphogypsum, which has been in the dumps for more than 5 years, showed that by its quality indicators it can be attributed to the 2nd grade in accordance with GOST 4013-2019, and the specific effective activity of the material (Aeff) corresponds to the I class of materials, which makes it suitable for the production of gypsum binders. Prototypes-cylinders were made from a mixture of phosphogypsum with lime dust of 1:1 composition at a pressure of 30 MPa and then subjected to hardening according to three schemes, in order to separate the passage of various types of hardening and study each of them for the physico-mechanical properties of the resulting material. The analysis of experimental data made it possible to establish the effectiveness of simultaneous flow in the system of two types of hardening – carbonate and hydration for lime and phosphogypsum components of the raw mixture, respectively. As a result of the organization of a mixed type of hardening of gypsum-lime binder, samples with a compressive strength of 26.5 MPa and a softening coefficient of 0.63 were obtained within 90 minutes. The calcium carbonate formed in the process, which is the product of the reaction between calcium hydroxide and carbon dioxide, significantly increases the water resistance of the hydration products of gypsum binder. It is established that with an optimal combination of technological factors and hardening conditions, a significant increase in the physical and mechanical characteristics of the carbonized material is possible in a short time.
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STRUCTURE FORMATION OF C-S-H FROM THE POSITION OF MICROMECHANICS OF COMPOSITE MEDIA

https://doi.org/10.34031/2618-7183-2021-4-5-5-15
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 5-15 p.
Abstract
The creation of an environmentally friendly building material to protect the human environment can only be carried out from the position of a transdisciplinarity approach, taking into account modern achievements in geomimetics and micromechanics of composite media. A wide range of basalt-fiber-reinforced concrete based on composite binders has been developed, which have increased characteristics of impermeability and durability under extreme operating conditions. The nature of the influence of the composition and manufacturing technology of cement composites on the pore structure of the composite has been established, which has a positive effect on the characteristics of gas, water and vapor permeability. High early strength was obtained, which allows the use of materials for operational repair and construction in emergency situations. The positive influence of the composition of the developed composite on the performances has been proved. The water resistance of the modified composite provides a water pressure of 2 MPa for 148 hours, which corresponds to the W18 grade (for the control sample – W8), the frost resistance grade – F300. It was found that the water absorption of the modified concrete samples was lower than that of the control sample, which is explained by the decrease in the pore structure index λ by 28.4 times, and the average pore diameter by 3.05 times. The total pore volume of the modified concrete was lower and decreased with increasing dose of nanosilica.
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DYNAMIC CALCULATION OF THE PLANE ELASTIC “DAM-FOUNDATION” SYSTEM

https://doi.org/10.34031/2618-7183-2021-4-5-16-23
 16-23 p.
Abstract
Design, construction, and reliable and safe operation of earth dams (more than 60 of them are in operation in the Republic of Uzbekistan located in seismic region) put forward requirements for the continuous improvement of the calculation methods for loads; as required by regulatory methods for fundamental (static) and special (dynamic) load combinations. These regulatory methods do not take into account the nonhomogeneous nature of the behavior and piecewise heterogeneity of the characteristics of foundation, and the stress-strain state (SSS) of an earth dam under constant or temporary loads, which is necessary for reliable and safe operation, especially in seismic regions. A general mathematical formulation of problems for earth dams in a plane elastic formulation is given. Dynamic calculations were conducted to determine the stress-strain state of an earth dam, taking into account the design features and real piecewise-nonhomogeneous physical and mechanical characteristics of soil of the structure body and base (these characteristics were provided by the design organization). The problem was solved by the numerical finite element method. The eigenfrequencies and modes of vibrations of the plane "structure-foundation" system are determined, considering the homogeneous and piecewise-nonhomogeneous characteristics of the foundation soil; the corresponding analysis of the behavior of the system was made. The stress-strain state of the “dam-foundation” system was investigated using calculated frequencies. The calculation results were lines of equal displacements (horizontal, vertical), normal and shear stresses in the “dam-foundation” system.
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EFFECT OF THE CURING CONDITIONS ON THE CHARACTERISTICS OF CITROGYPSUM-CONTAINING ALKALI-ACTIVATED BINDERS

https://doi.org/10.34031/2618-7183-2021-4-5-24-34
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 24-34 p.
Abstract
When hardening the binder system and it transforms into a consolidated conglomerate, the efficiency of the formation of the structural framework and the main operational characteristics of the final product dramati-cally depend on the thermal and humidity conditions of the environment medium, where the binder or raw material is consolidated. In this study, various conditions of hardening of binders with alkaline activation of various compositions were studied. Based on the literature analysis, the following were chosen as the hardening conditions for the experimental alkali-activated systems: 1) - thermal drying, which was carried out in an oven at a temperature of 60°C for 24 hours; 2) hardening in ambient laboratory conditions, at a temperature of 23 ± 2°С, relative humidity - 33 ± 2%. An aqueous solution of alkali NaOH and salt Na2SiO3 were used as alkaline activators. The resulted data of the change in the average density showed that when using an alkaline activator, heat drying promotes the compaction of the hardened composite (typical for both types of the alkaline component) by 5 and 7 % for NaOH and Na2SiO3, respectively. The absence of alkaline activators in the experimental samples leads to decompaction of the structure after exposure to thermal drying and a decrease in the average density to 18%. The experimental results showed that thermal drying contributes to an increase in the strength parameters of experimental samples of an alkali-activated binder using Na2SiO3 to 110% (from 1.9 to 4 MPa). For the rest of the samples, a significant decrease in strength is observed (more than 2 times). A visual analysis of experimental samples of alkali-activated binders showed that the binders containing the addition of citrogypsum showed clear signs of efflorescence in the case of their hardening in ambient laboratory conditions. At the same time, for similar compositions from a series of samples hardened under thermal drying conditions, there is a complete absence of this phenomenon.
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INFLUENCE OF MATERIAL STRUCTURE ON THE MAGNETOSTRICTIVE PROPERTIES OF A RADIATOR FOR DEFROSTING HEAT EXCHANGERS OF VENTILATION EQUIPMENT

https://doi.org/10.34031/2618-7183-2021-4-4-5-10
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 5-10 p.
Abstract
The article deals with the properties of ferromagnetics and their behaviour in an external magnetic field. The conditions under which magnetism occurs in materials are shown and the choice of material for a magne-tostrictive emitter is justified. The composition and properties of permendur as the most suitable material for the manufacture of magnetostrictive radiators are presented. It is shown that for the manufacture of the magnetostrictor it is feasible to use electro-erosion equipment for cutting packages from permendur compared to the costly and cumbersome method of stamping in a matrix of a particular shape. Tests were carried out on a duralumin heat exchanger with artificial frostbite. The evaporator was fed with refrigerant at 0.22 MPa, which corresponds to the boiling point of R 410a refrigerant at 35°C, by means of a refrigerant line made of aluminium pipes. Frostbite was then produced by applying moist air using an ultrasonic steam generator. Frost on the evaporator surface is discharged by means of a magnetostrictor mounted on the heat exchanger. The proposed method allows for the most effective cleaning of the surfaces of heat exchangers of ventilation equipment from scale, fouling and other mechanical deposits by means of mechanical vibrations.
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INFORMATIZATION OF CONSTRUCTION MANAGEMENT AS A BASIS FOR PREVENTING MAN-MADE ACCIDENTS

https://doi.org/10.34031/2618-7183-2021-4-4-11-31
 11-31 p.
Abstract
The article presents the principles and algorithms of the finite element method in solving geotechnical problems taking into account seismic impacts for determining the stress-strain state of structures and slope stability, implemented in the Midas GTS NX software package. GTS NX allows you to perform calculations of various types of geotechnical problems and solve complex geotechnical problems in a single software environment. GTS NX covers the entire range of engineering and geotechnical projects, including calculations of the "base-structure" system, deep pits with various mounting options, tunnels of complex shape, consolidation and filtration calculations, as well as calculations for dynamic actions and stability calculations. At the same time, all types of calculations in GTS NX can be performed both in 2D and in 3D. The author does not claim to be the author of the finite element method, but he cannot do without pointing out the basic equations, as this affects the definition of the boundaries of use, the formulation of algorithms for constructing calculation schemes and the analysis of calculation results.
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DEVELOPMENT OF A TECHNOLOGICAL PROCESS FOR MANUFACTURING WELDED STRUCTURES (RETRACTED 28.10.2021)

https://doi.org/10.34031/2618-7183-2021-4-5-35-44
 35-44 p.
Abstract
The main goal of this article is to obtain welded permanent joints of modern thermally hardened aluminum and aluminum-lithium alloys made by laser welding, having mechanical characteristics (temporary tensile resistance, yield strength, elongation at break) and structural-phase composition close to or equal to the base alloy. It is shown for the first time that by controlling the parameters of heat treatment of samples with a welded joint of all studied aluminum-lithium alloys, it is possible to purposefully influence the formation of the specified mechanical properties of the weld by changing the structural and phase composition of the weld. The evolution of the structural and phase composition of welded joints of thermally hardened aluminum and aluminum-lithium alloys has been investigated using modern independent diagnostic methods: for the first time, the use of synchrotron radiation diffractometry in combination with high-resolution transmission, scanning electron and optical microscopy. The dependences of the increment of deformation under cyclic loading with amplitudes exceeding the elastic limit on temperature are established. For untreated welded joints, it was found that at +85 °C, the inhomogeneity of the deformation increment increases, and its speed increases by 8 times for alloy 1461, 5 times for alloy 1420 and 1.5 times for alloy 1441. At a temperature of -60 °C, alloys 1420 and 1461 have hardening stages, during which the value of deformation decreases at given boundary stress values. At +20 °C, there is a uniform increment of defor-mation and an increase in the amplitude of deformation with an increase in the amplitude of stress. At +85 °C, the strain amplitude does not change with increasing stress amplitude, its value is 0.55-0.5 of the strain amplitude at +20 °C. Based on the research results, technological techniques have been developed that allow obtaining mechanical characteristics and structural-phase compositions of welded joints close to the main alloy during laser welding of aviation thermally hardened aluminum and aluminum-lithium alloys of the Al-Mg-Cu. Al-Mg-Li, Al-Cu-Mg-Li, Al-Cu-Li systems.
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ANALYSIS OF THE EFFECT OF METHODS OF INTRODUCTION OF ORGANOMINERAL ADDITIVES INTO MORTARS ON FINE SANDS

https://doi.org/10.34031/2618-7183-2021-4-4-32-40
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 32-40 p.
Abstract
The use of technogenic raw materials in the production of building composites is an urgent direction in the technology of production of building materials in view of its economic efficiency, environmental effect and wide possibilities of their application. Recently, the issues of environmental safety in the production of building materials, the possibility of their processing and disposal have come to the fore. All this is dictated by the need for energy and resource conservation, the massive depletion of natural reserves and the progressive pollution of the environment due to anthropogenic activities. Construction composites provide ample opportunities for recycling of secondary raw materials, as their structure allows them to be used not only as a filler, but also in some cases as additives for regulating certain properties. More studied and widely used are ash and slag mixtures on the basis of which various organomineral additives are developed. So, on the territory of the Chechen Republic there are dumps of ash and slag mixtures, which, according to their chemical and mineralogical composition, are suitable for the design of organomineral additives and fillers in construction concretes and solutions. Building solutions are widely used for interior and exterior finishing works during the construction of construction projects in the Chechen Republic, which is characterized by high humidity in the winter, which provokes deformations of the plaster layer on facades. In this article, the development of an organomineral additive based on an ash-slag mixture is considered to improve the quality of mortar mixtures resistant to such conditions.
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EXPERIMENTAL STUDY OF PLATES FOR PUNCHING UNDER DYNAMIC LOADING

https://doi.org/10.34031/2618-7183-2021-4-4-41-48
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 41-48 p.
Abstract
The issues of strength and deformability of reinforced concrete floors during punching remain insufficiently studied at present, despite the available publications in the technical literature. This article presents the results of experimental studies on punching of fragments of conjugation of flat reinforced concrete monolithic slabs with a column under dynamic loading. The purpose of these studies was to obtain experimental data on the stress-strain state of a fragment of a monolithic floor during dynamic punching with varying thickness and class of concrete, to reveal the failure patterns of experimental samples, and to obtain new experimental data. A setup for dynamic testing is described. Comparison of breaking load for specimens tested under dynamic loading with breaking load for specimens tested for static load is presented. The angles of inclination of the punching shear pyramid under static and dynamic loading are indicated.
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