In order to clarify the effect of the MgO⁻silica fume (SF) ratio on the reaction process of the MgO⁻SiO₂⁻H₂O system, the reaction products and degree of reaction were characterized. Furthermore, the parameters of the reaction thermodynamics were calculated and the reaction kinetics were deduced. The results indicate that a large amount of Mg(OH)₂ and small quantities of magnesium silicate hydrate (M⁻S⁻H) gels were generated upon dissolution of MgO. However, the M⁻S⁻H gels were continuously generated until the SF or Mg(OH)₂ was consumed completely. For a MgO dosage less than 50% of the total MgO⁻SiO₂⁻H₂O system, the main product was M⁻S⁻H gel, while for a MgO dosage greater than 50%, the main product was Mg(OH)₂. The results indicate that M⁻S⁻H gels have greater stability than Mg(OH)₂, and the final reaction product was prone to be M⁻S⁻H gels. Based on the experimental values, an equation is proposed for the reaction kinetics of MgO.
Keywords: MgO; kinetics; reaction process; silica fume; thermodynamics.