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.