Process for treatment of gypsum or plaster

摘要

The procedure consists of heating the gypsum or plaster to a temperature of between 180 and 600 degrees C, cooling to a temperature of less than 120 degrees C in under three minutes, and preferably in a few seconds, e.g. by flash cooling, adding lime in a proportion of between 2 and 25 per cent by weight, and grinding the resulting mixture to give a grain size of between a few microns and 200 hundred microns. The lime can be added before the heating phase, which is regulated to control the variable proportions of anhydrite II and anhydrite III.