Carbonation-Induced Corrosion Assessment for Reinforced Concrete Structures

Abstract Rebar corrosion induced by carbonation of concrete can occur in structures in both wet and dry exposures. This corrosion can become increasingly relevant in buildings as housing structures age and concrete carbonation occurs. The corrosion risk can vary depending on inter-related factors that include design, materials, and environmental exposure. The risk of corrosion furthermore can be assessed by the corrosion initiation and propagation phases. In this work two sets of testing were performed, including large scale concrete column testing to assess the corrosion behavior of steel subjected to loading and small-scale concrete testing to identify the effect of material and moisture condition environments on carbonation penetration. Concrete was cast with different water-to-cement ratio, limestone aggregate size, and conditioned in various moisture environments. The concrete specimens conditioned in wet conditions maintained in extended accelerated carbonation conditioning for up to 1 month of continuous carbonation of near 100% CO2 at 20 psi did not yield any significant carbonation penetration due to the slow rate of CO2 penetration. Concrete carbonation for the concrete specimens maintained in the dry condition fully carbonated within 67 hours and significant carbonation occurred for the concrete specimens maintained at 75%RH. In the carbonated concrete, the corrosion rate ranged from 0.2-0.8 μA/cm2. In presence of an external compressive force, the corrosion rates were similar; however, the time to corrosion initiation was delayed in time by a factor of 1.6-2. It is evident that both corrosion initiation and propagation should be considered when establishing recommendations for structural health monitoring and inspection.