Modelling the impact of abundant geochemical components on phase stability and solubility of the CaO—SiO₂—H₂O system at 25°C: Na⁺, K⁺, SO₄^2-, Cl^- and CO₃^{2 -}

A model for the CaO—SiO₂—H₂O system at 25°C is proposed, and based upon this, more complex systems including the effect of SO₄^2-, Cl^-, CO₃^2-, Na⁺ and K⁺ on phase relations and solubilities in the title system have been calculated by thermodynamic modelling. At sea-water concentrations of NaCl, mixed sea-water-pore fluid compositions enhance the solubility of calcium from Ca(OH)₂ and C-S-H but do not otherwise affect the stabilities of these phases. Carbonate and sulfate, on the other hand, react strongly with cement substances both with and without sodium being present; the complex solubility and reaction paths are quantified. Comparison of calculated reactions with literature data are made where possible; generally good agreement is obtained.