Rate of heat evolution during the hydration of OPC, OPC-20 wt% FA, OPC-5 wt% CH and OPC-20 wt%FA-5 wt% CH in the presence of 0.2 and 0.5 wt% super plasticizer has been studied at 35 and 45 degrees C with the help of TAM Air isothermal calorimeter for 60h. The results have shown that hydration retarded in the presence of super plasticizer. Higher the concentration of super plasticizer, higher is the retardation. However hydration accelerated with the increase of temperature. Mechanism of hydration is discussed in this manuscript. (C) 2012 Elsevier B.V. All rights reserved.