Elmira Kalshabekova

This article explores the use of waste from polymetallic combines in South Kazakhstan, specifically tailings from the Achisay and Ansay deposits, as aggregates (crushed stone, sand) and mineral additives (dispersed barite powder) for producing concrete with specified operational properties. These secondary raw materials are now abundant in relation to their use, which makes them an affordable and accessible alternative for the manufacturing of concrete while also promoting environmental sustainability. X-ray diffraction, differential thermal analysis, and scanning electron microscopy of enriched barite ores in these tailings revealed valuable components, such as calcite, quartzite, and dolomite, suitable for use as aggregates and mineral additives. The calcite and quartzite content in the Ansay samples exceeds that in the Achisay samples. Concrete mixes with various proportions of crushed stone and sand from these tailings were prepared, and their working characteristics were analyzed. The impacts of filler content and grain composition on the characteristics of concrete mixtures were identified, and the requirements for optimizing aggregate grain composition to produce heavy concrete with desired qualities were determined. Heavy concrete with densities from 2300 to 2839 kg/m³ and compressive strengths from 41.6 to 58.2 MPa was developed. Physical and mechanical properties, including density, water absorption, frost resistance, and compressive strength, were also evaluated, confirming the feasibility of using technogenic waste in composite heavy concrete production.

This article considers the possibility of using technogenic waste from the mechanical processing of Sastobe carbonate rocks as coarse and fine aggregates in the production of heavy concrete. X-ray diffractometric analysis CaCO3 d = (3.849-3.14-2.49-2.277-2.088-1.912-1.869 A0) and the endothermic peak in the temperature interval of 800-850°C in the differential-thermal analysis curve technogenic residues formed during mechanical processing of Sastobe carbonate rocks showed that it mainly consists of calcium carbonate. Studies have shown that fine and coarse aggregates based on carbonate rocks have a rough surface, which increases their specific surface area and ensures a strong bond with the cement stone. At the same time, technogenic waste contains 2-3% powder fraction up to 0.16 mm, this fraction serves as an active mineral mixture. As a result of research, the use of these wastes as fillers can reduce the consumption of traditional crushed stone and sand by 50% without reducing the physical and mechanical properties of concrete, replacing 50% of traditional fillers with technogenic fillers based on carbonate rocks, increasing the density of concrete (2490kg/m3), reducing its water absorption (0.66 %), strength (49.8 MPa) and frost resistance (F400) indicators made it possible to obtain concrete that is the same as the control sample and to reduce its cost without reducing the physical and mechanical properties of concrete and to improve the environmental conditions of the region.

Shrinkage has a great influence on the operation of the heat accumulator design, therefore, when developing structures with heat storage materials, it becomes necessary to determine the pressure in a non-expanding (closed) storage structure from the compressibility coefficient of the material, which can be considered an operational characteristic of the material. The article presents data on shrinkage (and expansion) of the investigated heat-storage materials and a method for estimating the pressure that can develop in sealed battery structures completely filled with heat-storage materials in a crystalline state. It has been determined that, for the normal operation of structures with heat storage material, it is necessary either to create conditions in it that allow avoiding an increase in pressure, or when filling the structures of the accumulator of heat storage material, take into account the shrinkage of the material, or use heat storage material with melting temperatures lower than is required when working at atmospheric pressure. pressure.

This paper proposes a mathematical model and a procedure for calculating the thermal state of the enclosing structure of the building, which includes an energy-active panel that accumulates solar radiation due to the phase transition of the heat-accumulating material. The mathematical model is based on a two-dimensional non-stationary nonlinear equation of thermal conductivity, which describes the process of heat transfer in the bearing layer of the enclosing structure and the energy-active panel. The model also includes equations describing radiant heat transfer between opaque and translucent bodies. To correctly describe solar insolation, the ASHRAE 2009 model was used in conjunction with the daily change in the position of the Sun in the sky. To solve the system of equations that make up the mathematical model, an iterative procedure has been developed, which involves alternating solution at each time step of the two-dimensional equation of thermal conductivity and a set of algebraic equations of convective and radiant heat transfer. The study’s result established that the amount of accumulated energy in the heat-accumulating material of the phase transition during daylight hours increases significantly, from 15 to 35 %. At night, the surface temperature of the heat-accumulating element in structures using a material with a phase transition is greater than in the case of heat accumulation only in the bearing layer. As a result, it is possible to select from 70 to 120 % more accumulated heat while the presence of high-thermal partitions in a heat-accumulating material with a phase transition contributes to an increase in accumulated heat and usable heat