Clinkering and early age hydration characterization of Belite-Alite Calcium Sulfoaluminate (BACSA) cements

Abstract

In this work, four BACSA clinkers with different compositions (belite ~ 70-55 wt %, alite ~ 10-15 wt % and ye’elimite ~ 10-15 wt %) were synthesized (at laboratory scale). Lime, gypsum, kaolin and sand were used as raw materials and clinkering temperatures from 1280 to 1300 ºC were studied. Every BACSA clinker was chemically and mineralogically characterized through X-ray fluorescence and laboratory X-ray powder diffraction (LXRPD), the latter in combination with the Rietveld methodology to obtain the full phase assemblage including amorphous contents. The clinker with the targeted composition (belite ~ wt 60 %, alite ~ 13 wt % and ye’elimite ~ 10 wt %) was chosen to perform the scaling-up (5 kg). To do so, the processing parameters (milling time and clinkering conditions) have been optimized.

Finally, the hydration of the corresponding BACSA cement pastes (prepared with the scaled-up clinker and gypsum) was studied through rheological measurements (at very early hydration time), calorimetry and impedance spectroscopy (first 24 h), and LXRPD in combination with the Rietveld methodology and G-factor method, at 1 and 7 hydration days to determine degree of hydration.