we present the results of studies of vermiculite concrete composites with various silica components such as cinder, tuff sand and volcanic ash for fire protection of building structures. The study shows that introduction of saponified wood resin into the vermiculite concrete mixture improves its rheological properties and reduces the average density of the composite. Portland cement can replace up to 20-25% of the mass of ash, tuff sand and cinder without significant deterioration of the properties of vermiculite concrete. Dispersed basalt fiber reinforcement of cement vermiculite concrete increases the strength and fire-resistant properties of the initial matrix.

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The article presents the research results on of a trapezoidal wooden truss with ascending braces on metal tooth plates parametric optimization. A deterministic algorithm has been developed and a program has been compiled that allows you to find the optimal parameters of the truss from the condition of minimizing the volume of wood, for given initial conditions. The optimal parameters for a truss with a span of 24 meters at a given value of the external load are revealed, diagrams of the dependence of the objective function on the varied parameters are drawn.

Objectives. The aim of the study is to increase the physico-thermal and operational characteristics of heat-resistant ceramsite concrete with an activated binder by pre-heating the mixture.Method. To conduct the study, a technique was developed by the Research Institute of Concrete and Reinforced Concrete named after A.A. Gvozdev.Results. An analysis of the study results of the effect of preliminary electric heating on the physico-thermal characteristics of heat-resistant ceramsite concrete on the basis of a composite binder showed that, in comparison with drying at a temperature of 105º, the operational properties of heat-resistant ceramsite concrete are enhanced by uniform heating of the samples along the concrete body. This isdue to the pore pressure in the concrete structure being reduced by removing physically bound water. Ceramsite is used as large filler while ceramsite sand is used as small filler; activated composite combination of local mineral raw materials consisting of Portland cement and calcined argillic clay is used as a binder. In the concrete body, due to the removal of physically bound water caused by the decrease in pore pressure, the formation of cracks in the interporal partitions decreases, preventing the explosive destruction of heat-resistant ceramsite concrete and improves its physico-mechanical, thermal and operational characteristics. Activated composite binder based on the combination of Portland cement and fine ground argillite clay reduces shrinkage deformations and increases the concrete strength as well as its heat resistance. Concretes with activated composite binder are less susceptible to volume change during the heating process,contributing to greater preservation of concrete strength and structure due to lower stress levels caused by the temperature deformations.Conclusion. The composition of the developed heat-resistant ceramsite concrete allows its use for monolithic lining of the walls of a tunnel kiln for burning ceramic bricks, as well as various concreting furnaces for the construction industry. The conducted research demonstrates the possibility and expediency of using electric heating for the hardening of heat-resistant ceramsite concrete with a composite binder. The use of electric heating increases the strength of heat-resistant ceramsite concrete both before and after heating to high temperatures. Optimised modes of electric heating of heat-resistant ceramsite concrete with a composite binder are established.

The paper studies the influence of preheating on thermomechanical properties of heat-resistant ceramsite concrete based on activated composite binding agent. The basic composition of heat-resistant ceramsite concrete was used in the study. This composition included a ceramsite gravel of the Kizilyurt Ceramsite Plant as a large and small filler, as well as the composite binding composition of portland cement + impalpable ceramsite sand with the activation on a planetary mill Activator-4M. The use of light heat-resistant concrete instead of single-piece refractory materials in kilns of various thermal units will allow decreasing the material consumption by 30-40% and reducing heat losses by 25-35%. [8]. The use of local construction materials allows increasing the efficiency of concrete in comparison with imported refractory materials. The composition of light heatresistant concrete with large and small fillers from ceramsite gravel of the Kizilyurt Ceramsite Plant and the activated composite binding agent based on the portland cement of the Buynaksk Cement Plant with impalpable ceramsite sand is developed for the study. The activation of a composite binding agent effectively increases the reaction capacity of a binding agent and reduces the water cement ratio, which improves the performance of concrete [1, 2, 10] due to the reduction of chemically unbound water in concrete. We believe that the preheating of a mixture prior to drying at a temperature of 105°C effectively affects the performance of concrete and reduces its destruction due to the presence of chemically unbound water. This reduces the number of microcracks in the structure of a concrete due to intensified hydration of the activated composite binding agent. The optimum mode of preheating and its influence on thermomechanical characteristics of concrete is defined. The influence of a concrete mixture preheating on its thermomechanical properties and efficiency of the accepted method is analyzed.