Study of chloride ingress and initial reinforcement corrosion in saturated concrete: Application of reactive transport model

This study investigates chloride ingress and the attainment of steel depassivation conditions in fully saturated concrete exposed to seawater under long-term temperature scenarios. A coupled reactive-transport model is implemented in Toughreact by integrating multi-ion diffusion, thermodynamic aqueous speciation/mineral equilibria, kinetic dissolution-precipitation of major hydrates, chloride binding, and porosity feedback on the effective diffusion coefficient D e . The model is benchmarked against published long-term submerged chloride profiles to ensure realistic coupled transport-reaction behavior. Results show that non-Fickian near-surface features (chloride “drop” and subsurface peaks) can persist even under permanently submerged conditions, driven by a thin altered surface layer with reduced transport porosity/D e and diminished binding capacity (reduced bound chloride). Parametric simulations over 5-40°C (up to 50 years) demonstrate that higher temperature accelerates mineral alteration, alkalinity loss, and the advance of depassivation indicators. A consistent comparison of three criteria (free chloride, total chloride, and [Cl - ]/[OH - ]) shows that they may diverge when alkalinity, binding, and porosity evolve; thus, [Cl - ]/[OH - ] provides a chemistry-consistent depassivation index. For a representative cover depth of d=50 mm, depassivation conditions are reached within decades under warm exposure.