How Much Water Does Calcined Gypsum Contain?

摘要

Gypsum has been used in construction since antiquity. Currently stucco, screed, plasterboard, filler, and many more products for the construction industry are based on this binder. Gypsum, CaSO4·2H2O, is typically named dihy-drate in construction chemistry. In different calcination processes, CaSO4·2H2O is heated above 100°C, thus removing some of the crystal water, and hemihydrate CaSO40.5H2O, or so-called plaster of Paris or stucco is formed. It may also be found as the rare mineral bassanite. In nature, some deep-sea medusa use single crystals of hemihydrate for orientation. By the calcination of gypsum at higher temperatures, all the crystal water is removed and anhydrate, CaSO4, is formed. Huge deposits of gypsum and anhydrate occur naturally and are mined industrially. Most products are colloquially called gypsum, but are chemically hemihydrate, which is the most-produced inorganic compound worldwide. The structure and water content of hemihydrate is thus of huge scientific and economic interest.