Corrosion Propagation of Dry-Cast Reinforced Concrete Pipes Exposed to Simulated Field Environments

Abstract Dry-cast reinforced concrete pipes (D-RCPs) are sometimes used in Florida at places in proximity to the ocean or at locations with high chloride concentrations where the water table seasonally saturates the D-RCPs. Previous studies suggest that corrosion would initiate after sometime in service once the critical chloride threshold has been exceeded at the reinforcement. However, very little is known as to how corrosion would propagate under the environmental service conditions. Instrumented segments obtained from two different types of D-RCPs in which corrosion had already initiated were used to investigate the corrosion propagation stage. During the propagation stage in different exposures, reinforcement eventually reached negative potentials values (< -600 mVsce), which suggest mass transfer limitations. The specimens show no visual signs of corrosion such as cracks or corrosion products. Moreover, the apparent corrosion rate values measured via linear polarization resistance suggest high corrosion rate. No crack appearance so far, could be explained by the corrosion products filling the pore system and also due to the small diameter of the reinforcement or longer exposure is required. Although there might be mass transfer limitations present, the current demanded by the anode is being matched by a larger cathode area due to macrocell effects, since the high moisture conditions likely lowered the concrete electrical resistance and hence increased the throwing power. This trend might change and longer exposure is planned to determine if the corrosion rate might become lower as a result of oxygen depletion at the cathode. Additionally, selected specimens are planned to be terminated to verify corrosion extent.