Über das Hochdruckverhalten von Gips / On the Behaviour of Gypsum under High Pressure

Abstract

The decomposition of gypsum (dehydration) was studied in the pressure range 7.5-60 kbar and the temperature range 75—400 °C using a belt type apparatus. Surprisingly, gypsum is rather stable even at pressures greater than 20 kbar contradicting the results of a calculation of the space requirement of the competing phases (AII—CaSO4 + H2O; Hemihydrate + H2O). Only when rising the temperature, as the most important thermodynamic variable for this reaction, the kinetically controlled decomposition starts. No accelleration of the dehydration process under shear stress (simple squeezer device) could be detected due to the limited (not geological) time.