Thermodynamic prediction of complex hydration processes and verification by experiments for the Ca-Al-C (CA, calcite, water) and Ca-Al-S (ye'elimite, gypsum, water) systems

The solubility of relevant phases in the calcium aluminate cements with limestone and in calcium sulfoaluminate cements with gypsum indicate several potential phase assemblages which might be formed during hydration. Thermodynamic calculations and pore solution data indicate that initially the solution is oversaturated with respect to several phases and thermodynamically metastable phase combinations may form. Some initially formed metastable phase assemblages contain more phases than predicted by the Gibbs phase rule and gain less Gibbs free energy than the stable phase assemblage. Solubility curves are used to define potential phase assemblages, the associated potential Gibbs free energy gain, to plot possible kinetic paths and to evaluate their respective probability. If different kinetic paths are conceivable, the reaction occurs along the solubility of the initially formed stable phases, namely monocarbonate in the calcium aluminate and ettringite in calcium sulfoaluminate system.

Automated summary

This study analyzes the potential phase assemblages that may form during hydration in calcium aluminate cements and calcium sulfoaluminate cements based on thermodynamic calculations and pore solution data. It reveals that initially formed metastable phase assemblages contain more phases and have lower Gibbs free energy than the stable phase assemblage.