Mesoscale Numerical Study on Time-Dependent Nonuniform Steel Corrosion–Induced Damage in Recycled Aggregate Concrete Systems

This study investigates the chloride transport and resulting corrosion-induced damage to reinforced recycled aggregate concrete (RAC) using finite-element simulations. A two-dimensional five-phase mesoscale-level time-dependent analysis was performed and chloride ingress, corrosion behavior, and corrosion product expansion induced RAC cracking were simulated. Material properties of aggregates, adhered mortar (AM) to the aggregates, old interfacial transition zone (ITZ), new ITZ, and the cement matrix were modeled. A series of RAC specimens with varying levels of AM contents were studied. The results indicated that chlorides moved faster in RAC specimens with more AM. Consequently, corrosion initiated quicker and more corrosion products were generated during the corrosion propagation process. The corrosion products' expansion caused cracking that was more severe in RAC specimens, and increased with increasing levels of AM. In addition to the impact of AM content, aggregate shape and orientation effects on corrosion-induced cracking were explored through the meso-level modeling approach. A parametric study on the chloride diffusion coefficients of AM was also conducted. The results show that the impact of chloride transport properties of AM was insignificant when the AM level was low. This study provides important insights into the mechanisms of service life deterioration in reinforced RAC structures.