Thermal behaviour and inertia effect in calcium aluminate cement pastes with microsilica

Abstract

The main contribution of this research is the study of the effect of thermal inertia in the activation energy in calcium aluminate cement pastes. For this, several formulations of calcium aluminate cement pastes (CACPs) with 51 wt% and 71 wt% of alumina (Al2O3) were made at 0.4 water-to-cement ratio, and with additions of 0.0 wt% and 20 wt% of silica content. The characterisation was done using X-ray fluorescence and X-ray diffraction, and the behaviour of the phases with temperature was studied using thermal gravimetric analysis, including the corresponding derivative thermogravimetry (DTG). 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 analysed. The activation energies for dehydroxylation of the gibbsite were calculated based on the Kissenger–Akahira–Sunose method. The activation energy values obtained, in kJ/mol, for CACP71 – 0, 20 wt% and CACP51 – 0, 20 wt% silica content were 19.9, 6.37 and 19.8, 17.2, respectively. The influence of silica on phase formation, activation energies and the effect of thermal inertia is also analysed.