Ordered Water: Just how much water is there in calcined gypsum?
Wednesday, April 15, 2009 - 10:22
in Physics & Chemistry
(PhysOrg.com) -- Gypsum was used as a building material in antiquity and is still widely used as a binder in plaster, drywall, and spackling paste. Known as dihydrate in construction chemistry, gypsum is a water-containing calcium sulfate (CaSO4• 2 H2O). In various calcination processes, some of the water of crystallization is removed, resulting in calcined gypsum, or hemihydrate (CaSO4• 0.5 H2O). When this material comes into contact with water, it reabsorbs it and sets up. The structure and exact water content of hemihydrate have remained a matter of speculation.