Characterization of reaction products and reaction process of MgO-SiO2-H2O system at room temperature

In order to clarify the reaction process of the MgO-SiO2-H2O system, the heat evolution, pore solution chemistry and reaction products of reactive MgO/silica fume (SF) pastes cured at room temperature were characterized. Based on the thermodynamic calculations and the experimental results, the final products tended to be M-S-H gels (magnesium silicate hydrates) rather than Mg(OH)(2), and the Mg/Si ratio of M-S-H gels was in the range of 0.67-1.00. The pH value was increased with the dissolution of MgO and a large amount of Mg(OH)(2) generated in the first 3 days. M-S-H gels were generated gradually afterward until SF or Mg(OH)(2) were consumed completely. It should be noted that the pH value of pore solution played a key role on the formation of M-S-H gels. A proper pH value of pore solution (about 10.5) led to a high concentration of Mg2+ (0.18 mmol/L), eventually resulting in a high formation rate of M-S-H gels. (C) 2014 Elsevier Ltd. All rights reserved.