sulphate resistant cement

Ordinary Portland cement does not resist the sulphatic action to a large extent . Disintegration due to sulphatic action is due to the presence of tri-calcium aluminate which reacts with sulphates and forms sulpho-aluminates and causing swelling and disintegration . To make cement more sulphate resistant percentage of C3A is reduced whereas C2S is increased . Rate of hardening of this cement is slow and requires longer period for curing . To offset the slower rate of hardening duew to changed chemical composition , sulphate resistant cements are ground a little finer than ordinary cements .