The mortar specimens made from Sulphoaluminate cement have good resistance to sulfate erosion. The appearance of the specimens is intact with slight expansion, and the water-cement ratio has little effect on their resistance to erosion. Both SAC-1 and SAC-2 show no obvious decreasing trend in flexural strength in the R2 erosion solution, and can maintain a high erosion resistance coefficient after a 12-month aging period. However, the strength of SAC-1 with lower water-cement ratio fluctuates with aging, while that of SAC-2 with higher water-cement ratio remains relatively stable. This is mainly because the late hydration of Sulphoaluminate cement will generate AFT with volumetric expansion characteristics, which will cause a large number of micro-cracks inside the cement paste, leading to a decrease in flexural strength of the specimen. The further hydration of AFT will fill these micro-cracks, resulting in an increase in flexural strength of the specimen. The flexural strength and erosion resistance coefficient of the specimens in R2 change with aging.
The erosion resistance of the mortar specimens made from Sulphoaluminate cement to magnesium sulfate has no significant change in appearance, but it is greatly affected by the water-cement ratio. The mortar specimens with a water-cement ratio of 0.3 (SAC-1) show no decrease in flexural strength in the R1 erosion solution, and can maintain a high erosion resistance coefficient after a 12-month aging period, demonstrating a good erosion resistance. However, the flexural strength of the mortar specimens with a water-cement ratio of 0.5 (SAC-2) starts to decrease after a 4-month aging period in the RI solution, and the erosion resistance coefficient K=0.6＜0.8 after an 8-month aging period, indicating a loss of erosion resistance capability. The flexural strength and erosion resistance coefficient of the specimens in R1 change with aging.
The mortar specimens made from Sulphoaluminate cement can basically resist the erosion and damage caused by high concentration magnesium sulfate. The specimens may appear to peel off and chip, but the erosion resistance coefficient of both SAC-1 and SAC-2 is greater than 0.8 after a 12-month aging period, indicating that they have not lost their erosion resistance capability. The flexural strength of the specimens increases parabolically with aging. After the test starts, the flexural strength of the specimens tends to increase. SAC-1 reaches its peak value after 8 months of aging, while SAC-2 reaches its peak value after 6 months of aging, and then the flexural strength decreases. The decrease in flexural strength in the later stage of the test indicates that the specimens have been eroded and damaged to a certain extent, and the erosion and damage may increase with aging, eventually leading to a loss of erosion resistance capability. However, due to insufficient data, a precise judgment cannot be made. Reducing the water-cement ratio can improve the erosion resistance of the specimens to some extent. The time when the flexural strength of SAC-1 starts to decrease is delayed by 2 months compared to SAC-2, and its erosion resistance coefficient is also slightly higher than that of SAC-2. The flexural strength and erosion resistance coefficient of the specimens in R3 change with aging.
