Kinetics of Tricalcium Silicate Hydration in Diluted Suspensions by Microcalorimetric Measurements

Investigations of tricalcium silicate (C₃S) suspensions using different techniques have shown the initial hydration kinetics of C₃S are strongly dependent on the water/C₃S ratio. In order to provide new experimental data on the hydration, we have adapted a Tian-Calvet heat flow isothermal microcalorimeter to study thermal flow variation released by C₃S stirred suspensions in water and saturated lime water. We observed three exothemic peaks and one endothermic peak. Their relative magnitude and duration depend on the W/C ration and the lime solution concentration. The protective layer theory appears to be consistent with our results for high W/C ratio. Moreover, portlandite precipitation seems to be a consequence and not the cause of the acceleratory period.