Hydration study of slag-blended cement based on thermodynamic considerations

Thermodynamic calculations, using the geochemical code PHREEQC coupled with empirical equations for kinetics of cement hydration and slag reaction, were carried out to predict the compositions of the hydrate assemblage and pore solutions of hydrating Portland cement and cement blended with slag and the blended cement containing limestone. The predicted compositions of hydration products and element concentrations in pore solutions compared well with experimental data reported in literature. The calculation results showed the varying Ca/Si and Al/Si ratios of calcium aluminosilicate hydrate (C-A-S-H)(1) in the hydration products due to hydration and slag addition. Limitations on the equation for reaction of slag and the importance of a C-A-S-H solid solution model in prediction of hydration products are discussed