Ceramics-Silikáty 36, (2) 105 - 108 (1992)

The DHA method was used to investigate the sequence of reactions taking place in aqueous suspensions of mixtures of tricalcium silicate and gypsum, at heating rates of 1 to 10 °C/min. The first product to form is crystalline hydroxylellestadite Ca₁₀(SiO₄)₃.(SO₄)₃(OH)₂, and after the calcium sulphate has been spent, calcium hydrosilicate C₃SH_1.5 is produced. Extrapolation to zero heating rate shows that hydroxylellestadite can already form at a temperature of 95 °C, and C₃SH_1.5 at temperatures higher than 160 °C. The size of hydroxylellestadite crystals is larger by an order of quantity than that of C₃H_1.5 crystals, and this is probably the cause of decreasing mechanical strength with increasing proportion of hydroxylellestadite in the reaction product.