Crystallization Kinetics of ?-Hemihydrate Gypsum Prepared by Hydrothermal Method in Atmospheric Salt Solution Medium

?-Calcium sulfate hemihydrate (?-HH) is an important cementitious material, which can be prepared by hydrothermal method from calcium dihydrate (DH) in electrolyte solution. Study of the conversion kinetics DH to ?-HH NaCl solution helpful for understanding control process. In this paper, X-ray diffraction (XRD) patterns were applied study effect temperature on crystallization determine kinetic parameters. The research results show that sigmoidal shape curve follows Avrami-Erofeev model, describes formation. Applying Arrhenius law experimental data and model calculations, apparent activation energy 124 kJ/mol nucleation 810 growth obtained. By adjusting solution, number steps increases, effectively increase DH-?-HH rate NaCI