Kinetic studies of tricalcium silicate formation from sol-gel precursors

Abstract

Reaction kinetic studies of Ca₃SiO₅ formation from sol-gel-derived precursors were carried out in situ using dynamic X-ray diffraction. Infrared spectra data, TEM experimental results, and X-ray diffraction patterns, all confirmed that CaO and Ca₂SiO₄ are the only compounds formed from a stoichiometric gel prior to Ca₃SiO₅ formation (< 1250 °C). The kinetic data for Ca₃SiO₅ formation are consistent with an Avrami nucleation and growth mechanism but with a sudden drop in the time exponent at higher conversion. The sharp drop of the exponent is attributed to the impingement of grain growth in the longitudinal direction and this is confirmed by SEM observations of the fully converted gels. The presence of 10% steam did not change the mechanism nor the activation energy of the reaction but significantly enhanced the nucleation and grain growth rate at both stages of the reaction.