The water of constitution remaining in the clay is not completely removed even after drying and this is removed between a temperature range of 430oC to 600oC. When we heat the clay, the water is slowly expelled out accompanied by a slight contraction. The expansion curves for slowly heated clays shows that kaolin’s and most clay undergo expansion up to 500oC to 600oC followed by a contraction. Where as montorillonites behave differently that beyond 100oC they only contract.
Water of constitution is not expelled from the clay substance uniformly and gradually. The endothermic and exothermic peak for natural clays reveals the presence of individual minerals in the clay. The endothermic reaction taking place below red heat is associated with the expulsion of water constitution from the clay substance.
To be contd…………..
