Influence of Repair on Corrosion-Failure Modes of Square-RC Columns Located in Tidal Zone

Abstract

Chloride-induced corrosion is the main cause of premature deterioration and failure of RC structures in corrosive environments. Therefore, modeling chloride permeation and investigating different methods for the repair and maintenance of RC structures exposed to corrosive marine environments are very important for optimizing the service life and life-cycle cost of these structures. This study introduces a prediction model for the chloride diffusion coefficient for portland cement (PC) RC under long-term exposure in the tidal zone of a marine site of southern Iran. A regression analysis (R2=0.9972) best fit was performed to check the accuracy of the prediction model based on Fick’s second law of diffusion. Various thickness equivalents for surface coatings were simulated as repair methods for the maintenance of RC structures exposed to corrosive marine environments. A finite-element model is provided for analysis to assess the time-dependent capacity of corroded RC structures using nonlinear analysis and the impact of corrosion on inelastic buckling of reinforcements. This analysis investigated and compared the influence of a number of repair or rehabilitation methods on the performance of a corroded square RC column due to chloride-induced corrosion, including concrete surface coatings used on the external surface of concrete, and increasing concrete cover thickness repair after the initial cracking of concrete cover. Results indicated that, compared with the no-repair scenario, the corrosion percentage of longitudinal bars of PC concrete with water-to-cement ratios of 0.35, 0.40, and 0.50 decreased 58.8%, 64.9%, and 71.7%, respectively, by increasing the concrete cover thickness by 7-mm; 53.5%, 59.9%, and 64.3%, respectively, by using epoxy polyurethane (PU) surface coating repair; and 52.3%, 57.4% and 63.0%, respectively, by using aliphatic acrylic (AA) surface coating. The AA surface coating had better performance in reducing the corrosion level of reinforcement than did the PU surface coating, which had better performance than increasing the concrete cover thickness by 7 mm.