Lightweight ceramic materials according to the aerated concrete technology using concentrated suspensions are produced. Pore formation in such slurries depends on rheological properties such as zeta potential, viscosity and pH. Reactions rate depends on the presence of definite minerals such as kaolinite, illite, smectite or low temperature modification of alumina. Grain size of raw materials and the sintering temperature have major influence on the pore structure of final material. These materials are used mainly as refractories but by using illitic or smectitic clays as thermal insulating materials.