Gypsum, one of the most used minerals on the world, can be found in mineral and rock form. The mineral form is in the shape of very large crystals. As for the rock form, Gypsum is found in the shape of thick residues of rocks. Furthermore, around 25% of the Gypsum production is provided as a derivative from industrial practices. But most of the Gypsum will continue to have a mining origin. In the cement production, there is no substitute for Gypsum.
Gypsum helps cement take a longer time to dry, because pure cement dries immediately. This makes things harder in the construction process because cement would turn solid before it is formed. It takes the role of a slowing down the solidification of cement until the right form is completed. Although gypsum of 75% to 85% is used in the manufacture of cement, yet a minimum of 82% CaSO4.2H2O is preferred. For every ton of cement, 0.04 to 0.05 ton of Gypsum is needed and after it is mixed with clinker, it is crushed to form cement. Additionally, Gypsum is used in the production of ordinary, pozzolana and blast furnace slag cement.