Understanding the hydration of dolomite in cementitious systems with reactive aluminosilicates such as calcined clay

This study investigates the hydration of dolomite, CaMg(CO3)2, with calcined clay in presence of calcium hydroxide and ordinary Portland cement. The hydration products as well as the microstructure at various ages were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and mercury intrusion porosimetry (MIP). Isothermal calorimetry was used to understand the reaction kinetics. The systems with dolomite were compared against control systems with limestone and quartz. It was seen that, the formation of carbonate - AFm phases takes place in the dolomite systems similar to limestone systems. No formation of brucite (Mg(OH)2) was observed till 90 days of hydration, with Mg2+ ions most likely being incorporated into hydrotalcite phase (Mg4Al2(OH)14). The synergetic effect observed in the Portland cement - calcined clay - dolomite system was found to result in a refined pore structure at early ages and improvement in the mechanical properties such as compressive strength.