Effect of carbonation curing on sulfate resistance of cement-coal gangue paste

This paper investigated the effect of carbonation curing on sulfate attack resistance of cement-coal gangue (PC-CG) pastes. Mechanical strength, volume deformation, and mass change of PC-CG blends were examined after different durations of sulfate solution immersion. On the other hand, the microstructure deterioration mechanism was determined using X-ray diffraction (QXRD/Rietveld), thermogravimetry differential thermal analysis (TG-DTA), mercury intrusion porosimeter (MIP), scanning electron microscope (SEM) measurements. Experimental results showed that accelerated carbonation improved the initial compressive strength before sulfate attack and alleviated the compressive strength loss with exposure to sulfate solution. The final compressive strength of carbonated specimens containing 0% or 10% coal gangue after 6 months of sulfate exposure retained 6.55% or 3.61% higher than those of the corresponding control mixtures before sulfate attack. In addition, the final compressive strength reduction of all carbonated specimens is much lower than those of the control specimens (8.69%∼34.19% VS. 12.93%∼47.52%). Moreover, the accelerated carbonation induced a decreasing expansion for every mixture (carbonated 2.32%∼6.11% VS. control 3.79%∼8.86%) partly due to the reduction of porosity and refinement of pore structure. Therefore, the combination of incorporating coal gangue and carbonation curing provides to a potential for manufacturing cement-based materials with better environmental sustainability and long-term durability in external sulfate attack regions.