Improvements in or relating to anhydrite or gypsum cementing compositions

摘要

A cement is prepared by adding to natural or artificially obtained anhydrite (dead burnt gypsum) or to hydrated calcium sulphate, dolomite which has been baked at a temperature from 600 DEG -900 DEG C. In one modification of the above process a mixture of magnesium oxide, with or without magnesium carbonate, and chalk or limestone is substituted for the dolomite. In another modification natural gypsum or anhydrite or a mixture thereof is added to dolomite and the mixture baked. A mixture of magnesium carbonate or magnesite and chalk or limestone may be substituted for the dolomite in this modification. In either of the above modifications sulphates of heavy metals or alkali metals may be added during the crushing of the materials if desired.