Gypsum and quartz sand are, for example, used in plaster and mortar. The gypsum content of the sample shows a two-step release of H2O from CaSO4*2H2O (dihydrate) into CaSO4*1/2H2O (halfhydrate) and finally into CaSO4 (anhydrite). This requires an entire energy of 122 J/g. Quantitative analysis reveals that the sample contained 23.4% of pure dihydrate. Between approx. 300°C and 450°C, the exothermic formation of β-CaSO4 with a released energy of 18.3 J/g occurred. The endothermic effect at an extrapolated onset temperature of 573°C is due to the structural α→β transition of quartz (crystalline SiO2).
The graph shows the result of an RUL test on a test piece taken from a fireclay brick (approx. 35% Al2O3);Test conditions: 0.2 N/mm2; 5 K/min; static air. At 960°C the test piece reaches its maximum expansion. Deformations of 0.5%, 1.0% and 2.0% have been achieved at 1210°C (T05), 1240°C (T1), and 1270°C (T2) respectively.