Activation of anhydrous calcium sulfate in the composition of fluorine-anhydrite

Abstract

In the process of mass production of materials based on anhydrite binders the application of fluorine-anhydrite - the waste obtained during the production of hydrofluoric acid, becomes economically profitable. Sulfates of alkaline earth metals, Portland cement and fine sulfate-containing additives were used to activate fluorine-anhydrite. Water-resistance was elevated due to decreasing porosity of hardened material. For that super plasticizers of latest generation Melflux 1641, Melflux 265t, Melment F15C were applied to prepare mixtures. Physical and chemical investigations of the structure of anhydrite compositions revealed the possibility to adjust the morphology of crystal-hydrate phases and increase the contact surface between them due to the formation of orientation-structured envelope with improved water-resistance in boundary layers. When selecting the corresponding hardening activators, types of super plasticizers and their concentrations, the compression strength of anhydrite compositions was changing in the wide range from 10 MPa up to 38 MPa.