Aren’t concrete retarder and gypsum retarder a kind of retarder?

The last process of cement production is to grind the cement materials and gypsum together, in which gypsum (calcium aluminate dihydrate) is generally added About 5% (equivalent to 1~3% SO3), which acts as a retarder. The mineral tricalcium aluminate (C3A) in cement hydrates very quickly. If gypsum is not added to slow the setting, the…