Evolution of hydration process of cement-based material containing high volume of dolomite powder

This study focused on the evolution of hydration process of cement-based material containing high volume of dolomite powder. The hydration products, microstructure, morphology and mechanical property of cement-based material blended with dolomite powder were investigated by means of isothermal calorimetry, X-ray diffractometry (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and universal testing machine. At early stage of hydration (1 day), high volume of dolomite powder accelerated cement hydration due to the fact that the surface of dolomite powder provided much more nucleation sites for C-S-H. As a result, the compressive strength of cement mortar incorporating dolomite powder increased significantly (up to 31.5%). At later stage of cement hydration (90 days), the reaction between dolomite powder and portlandite from the hydrated cement formed a small amount of magnesium hydroxide which led to the refinement of the pore structure and an increment of compressive strength. Besides, the tight packing of cement particles (D50 = 11.37 um) and finer dolomite powder (D50 = 6.45 um) contributed to the refined structure and the improvement of the compressive strength as well.