CARBONATE-CONTAINING CLAYS IN BRICK-MAKING MIXES - OPTIMIZATION WITH RESPECT TO FROST-RESISTANCE

An experimental investigation followed by mathematical modelling has b een performed to determine the maximum content of sandy-carbonate clay material which may be added to brick-making mixes to achieve a frost resistant product. A series of mixes with variable composition were pr epared and fired at 960 degrees C and 1000 degrees C respectively and were then tested for water absorption and diametral strength. The samp les were exposed to a freezing and thawing cycle and those which passe d the cycling were tested for diametral strength. Mathematical models for the measured characteristics as a function of raw material composi tion were determined using regression analysis and the database was re fined by microstructural studies. The models were optimized using geom etric programming and the optimum quantity of carbonate-containing cla y was determined. The predictions were proved by experiments.