Hydration of Portland cement is a heat that generates by chemical reaction between the cement with water. The release of heat will help accelerate hardening. But after hardening occurs, the part that has been hardened distribute the heat so that the slow nature of the possible occurrence of cracks in concrete. Hydration process in GGBFS/GGBS Cement does not react as quickly as Portland Cement. Concrete will produce more slowly heat by mixing GGBFS/GGBS on Portland Cement and peak temperature of concrete can be reduced. This is an advantage when the thermal cracking would be a problem in the manufacture of concrete.