Influence of the synthesis process on the reactivity to water of CaSO4-II: the role of the specific surface and microstructural disorder

Analysis of the process used to hydrate orthorombic anhydrite (CaSO4-II) obtained by the heat treatment of gypsum has shown that its reactivity is closely related to its specific surface. If, however, the BET surface is greater than 6-7 m2/g, reactivity is also dependent on the degree of microstructural disorder. These two parameters in turn are closely dependent on the thermal treatment for synthesis.