Highly porous building ceramics based on «clay-ash microspheres» and «zeolite-ash microspheres» mixtures

The possibility of obtaining highly porous heat-insulating ceramic materials based on compositions of mineral binding components (clay and zeolite rock) with ash-containing waste from the combustion of solid fuel (ash microspheres) is considered. It has been established that the pore-forming effect of ash microspheres in mixtures with low-melting clay is due to both the porous macrostructure of the ash component (the presence of hollow spherical particles) and the nature of physicochemical processes in the “clay – ash microspheres” and “zeolite – ash microspheres” systems (the synthesis of anorthite and mullite proceeding with an increase in molar volume). The creation of highly porous ceramic structures from mixtures of ash microspheres with zeolite rock, in addition to the structural features of microspheres, is also due to the structural (channel) porosity of zeolite minerals. The established pore-forming effect of zeolite rock and ash microspheres made it possible to develop a method for preparing a semi-dry masses from these compositions and to propose a technological scheme for obtaining a highly porous ceramic brick. The use of zeolite rock as a binder in a mixture with ash microspheres in content up 60–95 wt%, modified with zeolite-lignosulfonate slip, makes it possible to obtain a highly efficient constraction and thermal insulation ceramic brick with a compressive strength of 18–30 MPa, volume weight 930–1100 kg/m3 and thermal conductivity 0.22–0.31 W/m·K at a firing temperature of 950–1000 °C.