What is Gypsum?
Chemically known as “calcium sulphate dihydrate”, gypsum (CaSO4·2H2O) is a soft sulphate mineral containing calcium, sulphur bound to oxygen and water. It is a by-product of the evaporation of lake and seawater and, in its natural form, occurs in sedimentary rock formations.
The non-toxic material has been used in the construction industry as far back as ancient Egypt and is still very prevalent today – especially in countries such as Spain, England, Turkey, Russia and the USA.
Gypsum is used mainly to create dry walls, plaster and plasterboards. It is also used as the base for cement; to treat agricultural soil; and even in tofu. The rock is mined or quarried then crushed and ground into a fine soluble powder. In a process called calcining, gypsum powder is heated to approximately 350 degrees F, driving off three fourths of the chemically combined water. The calcined gypsum, or hemihydrate, becomes the base for gypsum plaster, gypsum board and other gypsum products.
An effective alternative to natural gypsum is superficial gypsum (FGD) which is a by-product of flue-gas cleaning in fossil fuelled power stations.