Despite many studies were carried out to understand the mechanisms controlling the kinetics of cement hydration, it is not completely well-understood and discussions are still open and controversial.The present research aims at acquiring a better understanding of these mechanisms and of the limiting factors of the characteristic periods observed by calorimetry, slightly simplifying the problem by studying hydration of pure tricalcium silicate (C3S) instead of real cement.Four C3S pastes were produced by mixing C38 powder with pure water or with mixes of water and isopropanol (with isopropanol contents of 7.5, 17.5 and 25 vol%) with a constant liquid/solid ratio of 0.5.Isopropanol was chosen as the inert solvent to replace water due to its weak impact on the microstructure.