Sergey Isachenko's research while affiliated with Moscow State University of Civil Engineering and other places

The current state of the building ceramics production is based on the following facts. Firstly, as a result of market conditions, the number of operating ceramics factories has significantly decreased. Secondly, considering the increase in the house construction rate due to the shift to new financing mechanisms, there has been an increase in the ceramic brick production by 2-3% since 2019. Growth opportunities are associated with higher thermal efficiency of ceramic products and masonry based thereon. The research objective in this article was the development of compositions for wall heat-efficient ceramics based on loess low-grade loams with the use of rice straw as a burnout additive and, in particular, the determination of the optimal processed rice straw consumption. The scientific novelty of the research consisted in the development of a method for selecting the ceramic mixtures composition, optimizing the composition and substantiating the rice straw and rice straw ash influence on the ceramic mixtures and products properties. Rice straw is introduced into clay masses at the preparation stage in an amount of 5-15% (by mass) of fluff rice straw, which burns out with burning temperature of 200-300°C and makes the mass porous, preventing shrinkage and forming ash containing up to 20% of amorphous silica. Carbonates in clay dissociate during firing, interacting with amorphous silica and forming various calcium silicates that strengthen the shard structure.

The energy efficiency concept incorporates energy conservation and durability components involved in the operation of buildings and cost considerations pertaining to the manufacturing and installation of materials. Ceramic brickwork offers the highest reliability and durability category, is not combustible and in terms of these parameters has advantages over other insulated facade cladding systems. Improving the thermophysical properties of masonry made of calcined ceramic products is possible through the use of heat-efficient ceramics and, in particular, porous ceramic stones. It is notable that the use of combustible additives does not enable the uniform distribution of porosity across the material while the high ash content of some additives reduces the quality of the ceramic crock. In this connection, it was decided that the use of exfoliated vermiculite of up to 0.5 mm fraction would be reasonable. A completed experiment made it possible to establish the optimal density of exfoliated vermiculite and a methodology based on the correlation between the properties of ceramic-vermiculite products and consumption of exfoliated vermiculite and ceramic product calcination temperature.

The methods of disperse reinforcement of a concrete matrix with the help of fibers make it possible to manufacture structures of complex configuration and solve problems of frost resistance of products. Fiber replaces secondary reinforcement, reducing the volume of use of structural steel reinforcement. Cellular fibrous concrete is characterized by high performance properties, especially increased strength in bending and stretching, impact strength and crack resistance. As a reinforcing component, it is preferable to use mineral fibers or thin basalt fiber. The use of polyamide fiber is allowed, but there are difficulties in forming adhesive contacts between the fiber and the mineral matrix of cellular concrete. A feature of mineral fibers is that they are high adhesive to the cement matrix. One of the promising types of dispersed bulk reinforcement of lightweight concrete is the use of expanded vermiculite. Expanded vermiculite can simultaneously be considered as a reinforcing component of a lamellar structure, as a component that reduces the density of the material and its thermal conductivity, as well as improves the fire protection performance. Expanded vermiculite can be used both in piece cladding products and as a part of dry warm and fire retardant plaster mixes.*

Gypsum-based binder modified by clay has properties close to the gypsum binder and can be used as plaster formulations or mortars. There are several reasons and chief among them is the lack of scientific based theory of formation and hardening properties of gypsum-based binder modified by clay without additives and that modified by additives. One of the classic ways of studying the mechanism of hydration of gypsum binders is the analysis of the heat liberation: hydration heat of the binder. With the thermos method of determining the heat liberation the ambient temperature is constant and the temperature of the sample which was at the beginning of the experiment changes as a result of the released heat of hydration of the gypsum; heat exchange between sample and the environment. Heat transfer is minimized through the use of thermos technology and effective insulation. The article presents the results of studying the dynamics of heat liberation during hydration of gypsum-based binder modified by clay without additives, with addition of superplasticizer and with the addition of setting retarder. Results in all cases are satisfactory. The highest degree of hydration evaluated by kinetics of heat liberation from a binder is with the addition of the superplasticizer. Application of setting retarder somewhat reduces the maximum degree of hydration and increases the hydration time. The degree of hydration of the binder with the addition of C3 additive and retarder is observed to be higher than that of gypsum-based binder modified by clay without additives. The studies confirm the possibility of using gypsum-based binder modified by clay in the composition of dry plaster mixtures for interior decoration works in premises.