The role of lime inclusions on the properties of fired clay articles

The effect of lime content or CaO/SiO2, molar ratio of the raw material on the physico-mechanical properties of the fired products was investigated in the range of 3 to 30\% CaO content (0.056 to 0.954 CaO/SiO2 molar ratio) and firing at 850 and 1150 degrees C for 2 h, with a heating rate of 1 degrees C/min. The sequence of the interactions occurring in the specimens made from clay/CaCO3, admixtures with different CaO/SiO2, molar ratios and fired at 850 and 1150 degrees C was determined and the existing phases were identified. The most effective eutectic acting on the lime-rich clay fired at 1150 degrees C was identified. This eutectic belongs to the lime-alumina - silica series having a fusion point of 1165 degrees C. The results show the great importance of the CaO/SiO2, molar ratio in determining the physico-mechanical properties of the fired-products by changing this ratio and firing temperature.