Fluoropgypsum belongs to type II anhydrous gypsum, which is characterized by: although it has hydration ability, the dissolution hydration rate is very slow, the setting time is long, the early strength is low, and generally can not be directly used as cementing material. In order to accelerate the conversion of type II anhydrous gypsum to dihydrous gypsum, it is necessary to modify the newly discharged fluoropgypsum.
Scholars at home and abroad have conducted extensive research on improving the hydration activity of anhydrous gypsum, and developed the activation technology of grinding, calcination and activator. The particle morphology, specific surface area and particle size distribution of anhydrous gypsum are different with different grinding methods, which has an important effect on the release of hydration activity. The increase of grinding fineness can significantly improve the hydration solubility. Calcination can distort the lattice structure of anhydrite and lead to the change of dissolution activity. Suitable calcination temperature can accelerate the hydration of anhydrite and shorten the setting time. Suitable activator can accelerate the hydration and dissolution rate of anhydrite, advance the crystallization time, refine the crystal and produce better gelling characteristics.
Professor IsraelD of Germany studied the relationship between hydration strength, flexural strength and microstructure of solidified anhydrite and found that the strength of anhydrite products is related to hydration rate, that is, the content in anhydrite, and the pore size plays a secondary role in the strength. Hu Hongmei 41 et al. studied the activation and modification of natural anhydrite, and the study showed that the fineness of anhydrite could be improved by extending the grinding time or mixing grinding AIDS, thus effectively stimulating the activity of anhydrite.
Huili Lu, Jicun Chen et al. 14849) calcined anhydrite on the basis of G-N-M-J quaternary composite excitation, and studied the influence of the dosage of foreign admixture and additional activator on the gelling property of gypsum in the composite excitation system. It was concluded that the setting time of anhydrite could be significantly improved by calcination above 100C, and the modification effect was the best at 100°C
