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.