Thermodynamics of MgO-MgCl2-H2O system

The thermodynamic reactions in the hydration, phase change and hydrolyzation process of MgO-MgCl₂-H₂O system were studied in this paper. The results show that Cl^- ion and pH value have significant influences on the phase stability of hydration products. In order to achieve a stable 5Mg(OH)₂·MgCl₂·8H₂O(5-phase) and prevent it from transforming into 5Mg(OH)₂·MgCl₂·8H₂O (3-phase), the dosage of MgCl₂ in reactants should be controlled to avoid the existence of too many free Cl^- ions in hydration products and the dosage of MgO should be increased to enhance the pH value of the system. Under the water curing condition, it is favorable to reduce the solubility of hydration products in water and maintain the stability of 5 phase that the pH value of solution is kept within a suitable range.