Coupled Cracking and Chloride Transport in Thin Ultrahigh-Performance Fabric-Reinforced Cementitious Matrix Systems for Durability Design

Abstract Reinforced concrete (RC) infrastructure exposed to marine environments and deicing salts suffers from premature deterioration due to chloride-induced corrosion, while existing strengthening systems often provide limited protection once cracking develops. This study investigates chloride transport in an innovative thin strengthening system based on an ultrahigh-performance fabric-reinforced cementitious matrix (UHP-FRCM), incorporating polyparaphenylene benzo-bisthiazole and carbon meshes embedded in a UHP matrix, under coupled mechanical loading and aggressive exposure conditions. Concrete disks and prisms were tested using rapid the chloride migration test, including tests under sustained flexural loading. Digital image correlation was used to quantify crack development and relate crack width to chloride transport. UHP-FRCM systems significantly improved durability compared to commercial systems, reducing apparent diffusion coefficients by up to 90% in uncracked conditions and limiting chloride ingress by up to 80% under loading, with penetration depths reduced to approximately 35 mm. Hybrid matrices combining steel and ultrahigh-molecular-weight polyethylene fibers provided the best performance by controlling crack width and disrupting transport pathways. A clear exponential relationship between crack width and chloride diffusion was observed. Service-life analysis based on apparent diffusion coefficients from accelerated tests indicates that UHP-FRCM systems can increase the predicted time to corrosion initiation at a 50-mm concrete cover depth by approximately 2.5–3.0 times compared with commercial FRCM systems, depending on the applied loading level. The findings demonstrate the potential of UHP-FRCM systems for crack-controlled durability design in chloride-exposed reinforced concrete structures.