2026 Volume 79 Issue 1 Pages 270-277
This study investigates the sulfate resistance of cements incorporating 10％ limestone powder replacement by mass and varying total alkali at 0.4％, 0.6％, and 0.8％ by adding potassium sulfate （K 2 SO 4 ）. Test method is based on ASTM C1012-24, monitoring length change and mass variation until a 182-day immersion in a sodium sulfate solution. The mortar specimens at 0, 91 and 182 days of immersion were analyzed using X-ray diffraction, thermo gravimetry, electron probe micro analysis, and mercury intrusion porosimetry to evaluate changes in the products and pore structure. The results showed that an increase in K 2 SO 4 proportion led to reduce the expansion and mass change. This suggests the possibility that the potassium incorporated into C-A-S-H is related to the suppression of ettringite formation. However, no proportional relationship was observed between the K 2 SO 4 content in the cement and the ettringite or gypsum formed in mortar specimens. Additionally, the total pore volume and the SO 3 penetration depth remained similar across all mixtures at 91 and 182 days, even though an increase in K 2 SO 4 proportion led to reduce total pore volume at the beginning of the immersion in a sodium sulfate solution. Further research is needed to understand the mechanism by which addition of K 2 SO 4 improves sulfate resistance.
