Strength and autogenous shrinkage of cement pastes added with surface-modified quartzite powder

The surface of quartzite powder was modified by autoclave method or low temperature calcination method through mixing with carbide slag. The mineral composition, surface profile and element composition of the surface modified quartzite powder were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM) combined with energy dispersive spectroscopy (EDS). The effect of surface modified quartzite powder on compressive strength and autogenous shrinkage of blend cement pastes were investigated. The microstructure of cement pastes was analyzed by using SEM and mercury intrusion porosimetry (MIP). The results show that tobermorite and β-C₂S phases are formed on the surface of the modified quartzite powder by autoclave method and low temperature calcinations method. Compounds with hydraulic activity are formed on the surface of modified quartzite powder, which can improve the interface structure between surface modified quartzite powder and cement paste, and further to enhance early strength and reduce porosity and autogenous shrinkage of cement pastes.