Role of concrete design parameters in preventing corrosion-driven failures in reinforced concrete structures

This study examines the synergistic deterioration mechanism in reinforced concrete structures subjected to the combined effects of inadvertently introduced chlorides and subsequent carbonation – a scenario increasingly encountered in inland regions due to the use of chloride-laden groundwater and suboptimal construction practices. While the individual roles of chloride-induced and carbonation-induced corrosion have been extensively documented, their coupled interaction leading to destabilization of bound chlorides and subsequent acceleration of steel corrosion – remains insufficiently elucidated. This research delineates the chemical processes by which carbonation decomposes chloride-binding phases such as Friedel’s salt and calcium silicate hydrate, thereby increasing the concentration of free chlorides in the pore solution under reduced alkalinity, which significantly enhances corrosion susceptibility. An experimental program was conducted to quantify the influence of water-to-cement ratio and concrete cover on reinforcement corrosion initiation under simulated cast-in chloride conditions and accelerated carbonation exposure. Electrochemical techniques, including half-cell potential mapping and galvanostatic pulse measurements, were employed to monitor corrosion kinetics, while depth-wise chloride profiling provided insights into the evolution of free chloride concentrations. The findings underscore the critical importance of concrete quality parameters in mitigating corrosion risk under combined degradation regimes and contribute to a more nuanced understanding of corrosion processes in complex environmental exposures.