Effect of water to cement (w/c) ratio and temperature profiles on the densification of C-S-H (calcium silicate hydrate gel) and hydration kinetics of triclinic tricalcium silicate (C3S) is studied beyond the first day of hydration. Calorimetry and quantitative X-ray diffraction/Rietveld analysis show that degree of hydration is unaffected by w/c up to 7days and marginally thereafter. Coupling the degree of hydration with the portlandite content measured from thermal analysis indicate that C/S ratio of C-S-H decreases with increasing w/c. There is a clear increase in the portlandite content with increasing w/c, even though the degree of hydration is unchanged, due to the variations in C/S ratio of C-S-H. On the other hand, when C3S is initially cured at a lower temperature (20 degrees C) and then at a higher temperature (40 degrees C), there is a significant increase in the reactivity even until 28days and vice versa. These experimental results were explained using the densified volumetric growth hypothesis, which assumes that hydration kinetics are dependent on the internal surface area of C-S-H.