Deterioration of Concrete Under the Combined Action of Sulfate Attack and Freeze–Thaw Cycles: A Review

The synergistic interaction between freeze–thaw cycles and sulfate attack induces a more severe and complex deterioration mechanism in concrete than either factor in isolation. This review elucidates this process by first examining the individual damage mechanisms and then integrating current research to analyze the coupled effects, revealing a complex process involving the superposition and competition of physical crystallization, chemical reactions, and fatigue stresses. The deterioration is delineated into four distinct stages: (1) Pre-Inflection Acceleration, (2) Post-Inflection Acceleration, (3) Deceleration, and (4) Rapid Failure. Experimental methodologies, research materials, and study protocols are critically examined, with particular emphasis on the influence of sulfate solution type and concentration, while highlighting significant discrepancies between laboratory conditions and field exposure. Based on this, the existing durability damage models and multi-physics numerical simulation methods are summarized, emphasizing the importance of cross-scale studies. Finally, prioritized research directions are proposed, emphasizing the need for refined experimental protocols and integrated physico-chemical models to advance predictive durability assessment. This work provides a foundational reference for guiding future research in concrete durability.