| Summary: | 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.
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