What does portland cement contain?
Portland cement contains about sixty per cent of lime, twenty five per cent silica and five per cent alumina. The other ten per cent consists of iron oxide and gypsum. It is the gypsum that regulates the hardening time or setting of the cement. Lime for making the cement is obtained from materials such as limestone, oyster shells, chalk and marl, which is a type of clay. The silica and alumina are obtained from shale, clay, silica sand, slate and blast furnace slag, while iron oxide comes from iron ore, pyrite and other such materials. How is cement produced?
