Chloride-Induced Corrosion Performance of ASR-Contaminated Concrete: Coupled Analysis Using Resistance Variation and NT Build 492 Method

This study examines how the Alkali-Silica Reaction (ASR) modifies chloride transport and chloride-induced corrosion (CIC) in reinforced concrete beams. Non-reactive and reactive concrete beams were cast with blue metal and dacite aggregates and subjected to a two-stage exposure: (i) alkali-rich immersion at 38 °C to induce ASR, and (ii) impressed-current CIC and NT BUILD 492 chloride migration testing. Microstructural changes were characterized using SEM-EDS and TGA. The reactive specimens developed extensive surface cracking, but after one year of ASR exposure, exhibited 47-53% lower non-steady-state migration coefficients (Dnssm: 7.03-8.02 × 10^-12 m²/s) than the non-reactive beam (15.09 × 10^-12 m²/s). After two years, Dnssm was reduced by approximately 37-56% (4.78-6.93 vs. 10.92 × 10^-12 m²/s). Crack mapping confirmed higher crack density and width in reactive beams, while SEM-EDS and TGA evidenced Ca depletion and the formation of C-(N,K)-S-H gels, which fill cracks and refine the pore structure. Electrical resistance monitoring showed earlier corrosion initiation in ASR-damaged beams but less pronounced resistance loss during the propagation phase. Overall, the results indicate that ASR can initially accelerate corrosion initiation through microcracking and reduced resistivity, but long-term gel deposition can partially seal transport paths and lower chloride migration under the specific conditions of this study.