A STUDY ON THE PHASE-TRANSFORMATION OF THE BASSANITES DURING HYDRATION

A real_time XRD analysis was carried out on the phase_transformation of α - and β -hemihydrate gypsums during hydration. The results indicate that the hydration rate for β -hemihydrate gypsum is greater than that for α -hemihydrate gypsum although the hydrates are the same dihydrate gypsum. The morphological characteristics of the dihydrate gypsums were researched by SEM. It is revealed that the size of the dihydrate gypsum crystals from α -hemihydrate gypsum was bigger than those from β -hemihydrate gypsum,and the former appears of short_bars in shape while the latter needle_like. Based on the observations it is concluded that the differences in hydration between the two bassanites are caused by the difference of their crystallinity that is controlled by the production techniques of the bassanites.