Decoupling chemical and physical sulfate attack on OPC and L.SAC concrete under wet-dry cycles

Fluctuating groundwater levels and tidal effects create unsaturated zones within the concrete, where varying moisture conditions like wet-dry cycles and partial immersion accelerate concrete deterioration. Chemical and physical sulfate attack (CSA and PSA) during wetting-corrosion and drying-crystallization processes are coupled, complicating the distinction of their individual contributions to concrete damage. This study conducted accelerated tests on ordinary Portland cement (OPC) and low-alkalinity sulfoaluminate cement (L.SAC) mortar specimens under wet-dry cycles and sulfate attack. The differences and similarities in macro performance deterioration and microstructural evolution between combined CSA and PSA, and sole PSA, were analyzed. The proportions of CSA and PSA in OPC concrete were quantified and the sulfate attack resistance of L.SAC concrete was revealed. Results showed significant differences in damage patterns between L.SAC and OPC specimens. In wet-dry cycles, L.SAC predominantly undergoes PSA, aligning with classical salt weathering theory, while CSA remains dominant in OPC concrete.