Thermal Behavior and Inertia Effect in Calcium Aluminate Cement Pastes with Microsilica

Abstract

The main contribution of this research is the study of the effect of the thermal inertia in the activation energy in calcium aluminate cement pastes. For this, several formulations of calcium aluminate cements paste with 51wt% and 71wt% of Al2O3 were made at 0.4 water to cement ratios, and with additions of 0.0wt% and 20wt% of silica contents. The characterization was done using x-ray fluorescent and X-ray diffraction, while the behavior of the phases with the temperature was studied through of thermal gravimetric analysis, including the corresponding derivative thermogravimetry. The influence of the thermal inertia on the activation energies and its dependence on the heating rate is established. The effect of thermal inertia on peaks of DTG curves and activation energies is analyzed. The activation energies for the dehydroxylation of the gibbsite were calculated based on the Kissenger-Akahira-Sunose method. The activation energies values obtained in kJ/mol, for CACP71 - 0, 20wt%; CACP51 - 0, 20wt% silica content, were 19.9, 6.37, 19.8, 17.2, respectively. The influence of silica on phases formation, activation energies, and the effect of thermal inertia is also analyzed.