Method for producing hydraulic binder based on hard gypsum III or α-type hard gypsum and hydraulic binder obtained by the method

摘要

A hydraulic binder is produced by firing gypsum and then rapid cooling the product from the firing temperature to below 80[deg]C in less than 2 minutes. Production of a hydraulic binder, which is based on natural or artificial calcium sulfate (gypsum, sulfo-gypsum, phospho-gypsum or titano-gypsum) and which contains more than 70% stable and soluble alpha anhydrite (anhydrite-III), is carried out by subjecting gypsum to (a) a firing or soaking step in which the gypsum is heated from ambient temperature to 220-350[deg]C; and (b) rapid cooling to below 80[deg]C in less than 2 minutes to stabilize the alpha anhydrite by fixing of its crystallographic structure. An independent claim is also included for a hydraulic binder acting as an alpha anhydrite based cement and obtained by the above process, the binder containing more than 70% stable and soluble alpha anhydrite.