Service life prediction of reinforced concrete marine structures under coupled chloride-induced corrosion and freeze-thaw cycles

The combined effects of chloride-induced corrosion and freeze-thaw cycles could lead to significant deterioration in the material and mechanical properties of reinforced concrete structures, compromising their serviceability and durability. This study experimentally investigated the effects of chloride-induced corrosion and freeze-thaw cycles, and their coupled action, on the mechanical response and damage evolution mechanisms of marine concrete specimens through rapid freeze-thaw cycling and impermeability tests. It is shown that the degree of surface damage in marine concrete specimens is more pronounced compared to their normal concrete counterparts. Both the freeze-thaw and impermeability resistance of marine concrete specimens are shown to be superior to those for normal concrete. The number of induced honeycomb pits and ratio of exposed coarse aggregates of marine concrete specimens under salted-freeze condition is more significant compared to those under water-freeze situation. The unfavorable deterioration effects of chloride-induced corrosion could accelerate the degradation of freeze-thaw and impermeability resistance of marine concrete specimens. In addition, in order to address the observed discrepancies between field and laboratory conditions, this study establishes, for the first time, a conversion relationship between the actual freezing and thawing temperature ranges and those defined in current design codes. This investigation also proposes deterioration models for marine reinforced concrete structures under coupled conditions of chloride-induced corrosion and freeze-thaw cycles. The effectiveness and applicability of the proposed deterioration models are validated and illustrated through service life assessment for the pier of an offshore highway bridge. Overall, the study provides experimental and theoretical basis for assessing the durability and service life of marine concrete materials and structures under coupled chloride-induced corrosion and freeze-thaw cycles.