ABSTRACT
Calcium sulfate exists as anhydrite (CaSO4), hemihydrate (CaSO4.'/2H2O), and dihydrate (CaSO4.2H2O). The known phases and forms of calcium sulfate are summarized in Table 11.1.
The A-II phase of anhydrite is the one that is thermodynamically stable up to 1180 °C, and converts to the A-I phase above this temperature. A third phase, anhydrite III, is metastable at any temperature; it exists in two distinct forms, designated a and ft.
