Portland slag cement is obtained by mixing Portland cement clinker, gypsum and granulated blast furnace slag in suitable proportion and grinding the mixture to get a thorough and intimate mixture between the constituents. It may also be manufactured by separately grinding Portland cement clinker, gypsum and ground granulated blast furnace slag and later mixing them intimately. The resultant product is a cement which has physical properties similar to those of ordinary Portland cement. In addition, it has low heat of hydration and is relatively better resistant to chloride, soil, water containing excessive amount of sulphates or alkali metals, alumina and iron, as well as, to acidic waters, and therefore, this can be used for marine works with advantage.
The manufacture of blast furnace slag cement has been developed primarily to utilise blast furnace slag, a waste product from blast furnace. The development of this type of cement has considerably increased the total output of cement production in India and has, in addition, provided a scope for profitable use for an otherwise qwaste product. During 98-99 India produced 10% slag cement out of 79 milion tons.
