A prediction model for chloride-ion ingress in concrete sleepers

There are approximately 600 km (370 mi) of railway passing through the desert areas in Iran. One of the important challenges associated with the degradation of railway structures in desert areas is chloride-ion invasion of the concrete, which causes the corrosion and swelling of bars, leading to the total destruction of concrete sleepers. Although numerous studies have been conducted on the prediction of bar corrosion in various reinforced concrete structures, there is no specific study on the prediction of bar corrosion in B70 concrete sleepers. This study investigates chloride diffusion in concrete sleepers and develops a prediction model using field and laboratory measurements. Sample profiles were taken from the Bam–Zahedan railway line for the determination of diffusion coefficients and initial and surface chloride contents. The early-age diffusion coefficient in concrete samples was obtained, and a prediction model was developed based on these parameters. Finally, a sensitivity analysis was performed in order to investigate the influential parameters on the initiation time of the corrosion. The results indicate that the effects of the chloride diffusion coefficient and the concrete cover were the leading factors in the corrosion initiation time.