A model for the variations in solution chemistry during tricalcium silicate hydration

A model to describe the variations in the composition of the aqueous phase during the hydration of tricaldum silicate has been developed. Multicomponent phase equilibria are used to model the manner in which the compositions of pore solutions change during hydration; the kinetics of hydration are not considered. Variations are considered in the aqueous phase during the hydration of tricaldum silicate and sodium-containing tricalcium silicate in water and in calcium sulphate solutions. The ternary system CaO-SiO₂-H₂O is used to describe the variations in the aqueous phase during the hydration of pure tricalcium silicate. The aqueous phase behaviour during the hydration of sodium-containing tricaldum silicate is considered with reference to the quaternary system CaO-Na₂O-SiO₂-H₂O. Finally, the hydration (jfsodium-containing tricaldum silicate in calcium sulphate solution is analysed. Rigorous treatment of the compositional variations in solution requires the use of the quinary system CaO-Na₂O-SiO₂-CaSO₄ -H₂O. However, the effect of silica can be ignored in this instance. The variations in the aqueous phase in this model system are compared to those observed during the hydration of Portland cement.