Chemical activation of clay in cement mortar, using calcium chloride

Clay exhibits pozzolanic activity, if it is used in high-strength Portland cement. The pozzolonic reactivity of the clay can be enhanced by various methods. In this work the effect of clay on the strength of cement has been investigated in the presence and absence of CaCl₂.2H₂O as a chemical activator. It was found that the strength of cement mortar has been significantly increased by using an aqueous solution of calcium chloride instead of water. The addition of CaCl₂.2H₂O decreased the evaporable moisture and pH of the extract as compared to the hardened cement paste, which shows enhanced pozzolanic reactions between lime and clay. The optimum clay replacement level was found to be 10% without activator and 20% in the presence of 4% CaCl₂.2H₂O. The parameters such as the strength development and water extraction showed that CaCl₂.2H₂O was a good chemical activator for a clay-cementitious system.