Communications of the American Ceramic Society Estimation of Thermochemical Data for Calcium Silicate Hydrate (C‐S‐H)

Calcium silicate hydrate (C‐S‐H) can be viewed as a solid solution, 0.833Ca(OH) 2 .SiO 2 .0.917H 2 O‐xCa(OH) 2 , at equilibrium at 30°C. On this basis, the change in Gibbsfree energy (ΔG r ) in the solid‐solution reaction was calculated from solubility duta for C‐S‐H in water. The change in ΔG r with real ratio decreased notably for the higher calcium contents (CaO/Si0 2 1.7; ×0.867). Thermochemical values for C‐S‐H (CaO/SiO 2 =1.7) were estimated to be ΔH°=‐2890 kJ/mol, ΔG°=‐2630 kJ/mol, and S°=200 J1/mol.K at 298 K .