Low Heat Cement

In the case of mass concrete structures such as dams , retaining walls , bridge abutments , rate of loss of heat of hydration from the surface is much lower than that generated . This causes rise in temerature inside the mass of concrete and may develop thermal and shrinkage cracks if proper precautions are not taken  . Under such cricumstances low heat cement . Calcium aluminate and tri-calcium silicate ar reduced while those of di-calcium silicate and Tetra-calcium alumino ferrite increased . By this measure the rate of evolution of heat of hydration is considerably reduced . Low heat cement has not only slower rate of heat generation but also greater resistance to cracking . In the initial stage of setting and hardening , rate of heat evolution of heat evolution is small as rate of chemical reaction is slow . But in the later stage rate of setting  and hardening is faster than ordinary cement . The ultimate strengrth attained by this cement is practically the same as that attained by an ordinary cement . The heat generated by ordinary cement in three days is nearly 80 calcories per gram of cement whreas for low heat cement it is of the order of 50 calories per gram of cement . This cement is manufactured only to special order and its initial setting time should not be less than 60 minutes . This cement offers greater sulphate resistance , due to decresed amount of tri-calcium aluminate . This cement is however not suitable for ordinary structure