FREE-ENERGY-BASED MODEL OF CHEMICAL-EQUILIBRIA IN THE CAO-SIO2-H2O SYSTEM

The chemical equilibrium between the C-S-H gel phase and the aqueous p hase in the CaO-SiO2-H2O system was modeled using the free-energy-base d Thermo-Gale commercial software system, Unlike programs that are bas ed on solubility products, the minimization of free energy allows the composition and solubility of the C-S-H phase to vary, as in real ceme ntitious systems. The C-S-H gel is modeled as a defect tobermorite str ucture, based on recent compositional data gathered using Si-29 NMR, T he composition is varied by removal of some of the bridging silica tet rahedra in the SiO layers and by incorporating different amounts of Ca in the interlayer spaces.