Effect of Clay Raw Materials on the Formation of the Microstructure of Cellular Concrete for Thermal Insulation Purposes

It is found that using sand and clay rocks of the incomplete stage of mineral formation as raw materials, it is possible to obtain effective autoclave cellular concretes for thermal insulation purposes. Improved rheological properties of the aerated concrete mix and a higher gas-holding capacity in comparison with lime-sand raw materials ensure the formation of a more uniform cellular structure. It is shown that the polymineral composition of raw materials provides the formation of gelled and highly crystallized phases, such as low-base calcium hydrosilicates CSH(B), hydrogranates and tobermorite, including alumina-containing ones, which optimizes the microstructure of the cementitious substance. At the same time, more dense inter-layer partitions than on lime-sand raw materials are formed, which increases the physical, mechanical and operational properties of thermal insulation materials. Increasing the number of phases in the composition of the cementing agent reduces its thermal conductivity. Micropores formed from finely dispersed highly crystallized phases also contribute to improving the thermal protection properties of heat-insulating autoclave cellular concretes on clay raw materials. The compressive strength, depending on the mineral composition of the rock at an average density of 350 kg/m³, increases by 7–23% in comparison with lime-sand materials, and the coefficient of thermal conductivity decreases from 0.09 to 0.075–0.065 W/m·°C.