Photoacoustic thermal characterization of kaolinite clays

The usefulness of photoacoustic techniques in characterizing the thermal pr operties of kaolinite clays, which are a very abundant mineral in some regi ons of Brazil, was investigated. Different behavioural patterns are observe d below and above a heating temperature of 950 degrees C and can be attribu ted to the change from metakaolinite to an amorphous three-dimensional mine ral which crystallises to mullite and crystobalite above 1200 degrees C. Th e implications of the results in the manufacture of clay bricks are briefly considered. This is important in tropical regions where a knowledge of the thermal properties of materials used in the building construction industry is highly desirable.