By adding gypsum to cement

Raw materials for cement-limestone, clay, gypsum. Cement is a diny greyish heavy  powder containing calciumaluminates and silicates.Gypsum (CaSO4.5H2O) is added to the components to increase the setting time of cement so that it gets sufficiently hardened. Setting of cement is an exothermic process and involves hydration of calcium aluminates and silicates.