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PERFORMANCES OF HIGH POROUS CELLULAR CONCRETE

https://doi.org/10.34031/2618-7183-2020-3-5-5-14
Abstract
The widespread use of cellular concrete for enclosing structures forces researchers to develop ways to improve their performance and durability. Compositions of aerated and foam concrete with the use of waste heat power engineering have been developed. The optimal formulation ratios have been identified that contribute to the creation of a rigid interpore matrix and water-repellent pore protection. The regularities of the synthesis of aerated concrete and foam concrete were established, which consist in optimizing the processes of structure formation through the use of a polymineral cement-ash binder and a pore-forming agent. The mix composition intensifies the process of hydration of the system, which leads to the synthesis of a polymineral highly porous heterodispersed matrix. The increased activity and granulometry of aluminosilicates predetermine an increase in the number of contacts and mechanical adhesion between particles during compaction, strengthening the framework of the interpore partitions. The mechanism of the influence of the composition of the concrete mix on the microstructure of the composite is established. The calculated sound insulation of airborne noise shows sufficient characteristics for using aerated concrete blocks as enclosing structures. One of the main advantages of aerated concrete is its low thermal conductivity, which is especially important from the point of view of ensuring the energy efficiency of buildings and structures. Even in spite of the high values of open porosity of the developed aerated concrete, the rigid frame makes it possible to achieve almost 2 times higher frost resistance characteristics than that of the reference specimen.
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DETERMINATION OF RHEOLOGICAL PARAMETERS OF POLYMERIC MATERIALS USING NONLINEAR OPTIMIZATION METHODS

https://doi.org/10.34031/2618-7183-2020-3-5-15-23
Abstract
The article is devoted to the problem of processing the experimental creep curves of polymers. The task is to determine their rheological characteristics from tests for any of the simplest types of deformation. The basis for the approximation of the experimental curves is the nonlinear Maxwell-Gurevich equation.
The task of finding the rheological parameters of the material is posed as a nonlinear optimization problem. The objective function is the sum of the squared deviations of the experimental values on the creep curve from the theoretical ones. Variable input parameters of the objective function are the initial relaxation viscosity and velocity modulus m*. A theoretical creep curve is constructed numerically using the fourth-order Runge-Kutta method. The nonlinear optimization problem is solved in the Matlab environment using the internal point method. The values m* and are found for which the objective function takes the minimum value.
To test the technique, the inverse problem was solved. For given values of the rheological parameters of the material, a theoretical curve of creep under bending was constructed, and the values m* and were found from it. The technique was also tested on experimental stress relaxation curves of secondary polyvinyl chloride and creep curves of polyurethane foam with a pure shear.
A higher quality approximation of experimental curves is shown in comparison with existing methods. The developed technique allows us to determine the rheological characteristics of materials from tests for bending, central tension (compression), torsion, shear, and it is enough to test only one type of deformation, and not a series, as was suggested earlier by some researchers.
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DEVELOPMENT OF RADIATION-PROOF CONCRETE COMPOSITIONS

https://doi.org/10.34031/2618-7183-2020-3-5-24-33
Abstract
The article considers the possibility of using composite binders and magnetite as components of concrete with radiation-proof properties. The use of the developed concrete is possible not only when it is necessary to build nuclear power plants, but also to create bunkers or anti-radiation shelters. A special feature of con-cretes used for the protection and design of nuclear reactor cranes is their properties, which they must have. These properties include: low thermal conductivity, increased density, high temperature resistance, reduced values of the coefficient of thermal expansion, shrinkage and creep. Technogenic raw materials for the production of very heavy concrete are studied, the main physical and mechanical characteristics, the requirements that need to be considered in the selection of raw mix composition for protective concrete are analyzed. The paper presents a comparison of physical and mechanical characteristics, the advantages and disadvantages of introducing a binder of various types: cement, cement with a superlasticizer and a binder of low water consumption. It was found that the use of a low-water-consumption binder increases the physical and mechanical characteristics while reducing the consumption of cement in the raw material mix compared to traditional heavy concrete with cement.
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EFFECT OF WOLLASTONITE ON THE MECHANICAL CHARACTERISTICS OF CONCRETE

https://doi.org/10.34031/2618-7183-2020-3-5-34-42
Abstract
Improvement of the physical and mechanical properties of cement composites should be accompanied by the disposal of industrial waste of various generation. Therefore, the paper proposes the principles of con-trolling the strength properties of concrete, which consist in the complex effect of wollastonite obtained from boron production waste on the processes of structure formation of the cement matrix. When this introduced in an amount of 2-8 wt. % wollastonite has a dual function as a mineral filler and a reinforcing fiber. It has been proven that in the presence of wollastonite, the concrete mix becomes lighter without reducing its physical and mechanical properties. It was revealed that the early strength for all the developed compositions with the addition of wollastonite increases due to the acceleration of hydration processes. Calcium silicate, which is wollastonite CaSiO3, has a close chemical composition with cement clinker, especially with Ca2SiO4 belite and Ca3SiO5 alite. This leads to the formation of a chemically homogeneous and, as a result, hardened microstructure. Elongated wollastonite fibers with good adhesion to the cement stone provide effective micro-reinforcement of the concrete composite. Using the results will lead to the possibility of designing high-strength concretes, including for special structures.
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DEVELOPMENT OF SPECIAL RECIPES OF BINDING COMPOSITIONS WITH IMPROVED PROPERTIES

https://doi.org/10.34031/2618-7183-2020-3-4-5-12
Abstract
Abstract: the ecological safety of earthly civilization suffers from the accumulation of huge volumes of industrial waste, the natural resource potential is decreasing, therefore, special attention is paid to the development of less costly and low energy-intensive technologies for obtaining new building materials, the implementation of which does not require high-temperature and expensive technological processing, and will allow the use of secondary and substandard raw materials.
The work presents the results of the development of special formulations of binder compositions of alkaline activation based on cement production wastes in the form of aspiration and clinker dust from electrostatic precipitators of rotary kilns and waste from the metallurgical industry - ferrosilicon additives in the form of active silica, which will allow obtaining new building materials with improved properties.
The paper investigates the properties of an alkaline cement paste and cement stone, reveals issues related to the theoretical foundations of the formation of the structure and strength of an artificial stone based on an alkaline activator. The research results, in our opinion, are certainly of practical importance for the construction industry, as the proposed formulations of clinker-free cements can partially replace expensive and energy-intensive Portland cement, making it possible to create strong and durable concrete and reinforced concrete structures.
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RESEARCH ON THE STRUCTURE OF CLAY RAW MATERIALS FOR CERAMIC PRODUCTS

https://doi.org/10.34031/2618-7183-2020-3-4-13-23
Abstract
Abstract: the research uses some methods for determining materials, strictly applying the current standards and requirements of the Russian Federation. The degree of scientific development of this research is that specialists of the Department of Engineering Physics and Materials Physics of Engineering Faculty of Bashkir State University and the laboratory of JSC "Ceramics" of the Republic of Bashkortostan conducted research in the field of ceramic materials science for construction purposes. The methodological basis of the research is based on well-known methods of studying the structure of clay raw materials suitable for the production of construction products, with the choice of a stable light range of products and eliminates cracking in the technological process of brick production. The correct composition leads to a reduction in energy consumption without compromising the physical and mechanical characteristics of products.
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INCREASING THE EFFICIENCY OF MINERAL POWDER FROM TECHNOGENIC RAW MATERIALS DUE TO ITS HYDROPHOBIZATION

https://doi.org/10.34031/2618-7183-2020-3-4-24-30
Abstract
Abstract: a promising direction in solving the problem of obtaining high-quality asphalt concrete is the use of mineral fillers, including from industrial waste.
The article considers the use of OEMK slag as a mineral powder in the asphalt concrete mix.
The influence of hydrophobization of mineral powder by GF Preparation on moisture absorption and its structuring ability to change the maximum shear stress from the content of mineral powder before and after hydrophobization was studied. It is established that the treatment of the filler provides the necessary hydrophobicity of the mineral material, reduces the bituminous capacity, water saturation, porosity of the asphalt binder, and increases its strength and water resistance. The results of studies of the main characteristics of asphalt concrete on the example of a mixture of type G III of the brand showed that as a result of hydrophobization, the strength, water resistance, water saturation, and swelling of the composite significantly increase.
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NON-PLASTIC RAW MATERIALS FOR THE PRODUCTION OF CONSTRUCTION CERAMICS

https://doi.org/10.34031/2618-7183-2020-3-4-31-38
Abstract
Abstract: research by some scientists shows that the most expensive element in the manufacture of construction ceramics are clay materials, in particular kaolins. They allow getting products with high strength, but at the same time increase significantly the mass refractoriness. In this connection, a significant amount of melt is added or the firing temperature is increased. Of course, this leads to an increase in the cost of products. In Russia, the reserves of these raw materials are insufficient and it is advisable to look for new non-traditional types of raw materials. There is a need to adjust the component composition of ceramic masses and use non-plastic raw materials. An example is natural wollastonites or their analogues in the form of diopside, which are a little-used type of mineral raw material. In the Siberian region, there are several deposits of non-plastic varieties of raw materials for the production of fired construction products. The most famous are the deposits of the Slyudyansky and Sayan districts. The authors present the results of analysis of diopside rocks, where the chemical, mineral compositions and behavior of samples under heating are studied. The absence of alkali and alkaline earth metal oxides in diopsides was determined. The content of iron oxide in the amount of 0.1% indicates the purity of the raw material. More than half of the composition is occupied by silica, which is 53% and 58% in the rocks of the Burutuysky and Sayan deposits, respectively. The basis of the mineral composition of the samples is diopside, with the presence of quartz, calcite, mica and magnesium carbonate. This range of minerals is traditional in many charges of ceramic materials. Therefore, the possibility of using diopside rocks in the production of building ceramic materials is quite high.
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ON INTEGRATED HEATING, VENTILATION AND AIR CONDITIONING SYSTEMS IN ROOMS OF SHOPPING CENTERS

https://doi.org/10.34031/2618-7183-2020-3-4-39-47
Abstract
Abstract: the paper considers a method for creating microclimate parameters in the rooms of shopping centers, sports complexes, etc. The possibility of using a complex system including air heating, ventilation and air conditioning is shown on the example of a shopping hall. To improve the efficiency of the system, it is proposed to replace traditional water heating with air heating, which works by using a gas burner-heat exchanger. For the rooms of a shopping center in the city of Saint Petersburg, the thermal engineering calculation of external fences was performed, and the heat capacity of the heating system was determined. Based on the results of the heat and air balance of the grocery shopping area, the performance of the ventilation and air conditioning system is calculated. An autonomous monoblock unit for air treatment was selected. During the cold period, the unit performs the functions of air heating and ventilation. Air recirculation is provided to save heat energy. The amount of outdoor and recirculating air is calculated. During the warm period, air is cooled and dehumidified by using a compression refrigeration cycle. The proposed integrated system for creating the required parameters of the microclimate allows reducing material costs by using a gas burner-heat exchanger instead of a heat point for water heating, as well as using a cheaper energy source and heat recovery through a heat pump.
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EFFECT OF POROUS STRUCTURE ON SOUND ABSORPTION OF CELLULAR CONCRETE

https://doi.org/10.34031/2618-7183-2020-3-2-5-18
Abstract
The compositions of gas and foam concrete with improved acoustic characteristics were developed. The optimal form of porosity, which contributes to the absorption of sound waves, both in the range of audible frequencies and at infrasonic and ultrasonic frequencies, is revealed. The mathematical model for designing sound-absorbing concrete was improved, taking into account both the porosity of the composite and the influence of the porous aggregate. The laws of synthesis of aerated concrete and foam concrete are established, which consist in optimizing the processes of structure formation due to the use of a polymineral cement-ash binder and blowing agent. The composition of the composite intensifies the process of hydration of the system, which leads to the synthesis of a polymineral heterodisperse matrix with an open porosity of more than 60%. Peculiarities of the influence of the “Portland cement – aluminosilicate – complex of modifiers” system on the rheology of the concrete mixture was identified, which can significantly reduce shear stress and create easily formed cellular concrete mixtures. The increased activity and granulometry of aluminosilicates predetermine an increase in the number of contacts and mechanical adhesion between particles during compaction, strengthening the frame of inter-pore septa. The mechanism of the influence of the composition of the concrete mixture on the microstructure of the composite is estab-lished. The presence of refined aluminosilicates and a complex of additives in the system along with cement contribute to the synthesis of the matrix with open porosity, thereby increasing the sound absorption coefficient.
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