Simultaneous Differential Scanning Calorimetry and Thermogravimetric Analysis of Portland Cement as a Function of Age

Abstract

We study the hydration and pozzolanic reactions of an ordinary Portland cement as a function of age, using the differential scanning calorimetry and thermogravimetry. The measurements are done for 2 days, 7 days, 28 days, 90 days, 180 days, and 360 days cured samples in order to monitor the rate of hydration. The investigation is performed in the temperature range from $$25\,^{\circ }\hbox {C}$$ to $$1000\,^{\circ }\hbox {C}$$ with a heating rate $$5\,^{\circ }\hbox {C}{\cdot } \hbox {min}^{-1}$$ in an argon atmosphere. The temperature, enthalpy, and mass change during the decomposition of calcium silicate hydrate gels, ettringite, portlandite, vaterite, and calcite are determined, and the changes in the portlandite amount are estimated in dependence on the time of hydration. We found out that the temperature and enthalpy of liberation of physically bound water, C–S–H gels and ettringite decomposition (all occurring from $$50\,^{\circ }\hbox {C}$$ to $$250\,^{\circ }\hbox {C}$$ ) and Portlandite decomposition ( $$420\,^{\circ }\hbox {C}$$ to $$530\,^{\circ }\hbox {C}$$ ) decrease with hydration time of studied samples. On the other hand, vaterite and calcite decomposition ( $$530\,^{\circ }\hbox {C}$$ to $$850\,^{\circ }\hbox {C}$$ ) the temperature varies and the enthalpy increases with hydration time of samples.