On the formation of thaumasite CaSiO3.CaSO4.CaCO3.15H2O: Part I

Thaumasite from a geological source was dissolved in distilled water at 8°C. The ionic concentrations in solution were measured after equilibration and a solubility product was calculated. The corresponding Gibbs free energy for the formation of thaumasite from the constituting elements at 8°C was calculated to be −7638 kJ/mol from the solubility product. The obtained datum allows a simulation of the formation of thaumasite in concrete. Results of the simulation are presented in part II and compared to experimental observations in part III of this report.