Reinforced Concrete (RC) structures under sea environments face challenges in achieving desired durability and performance during their designed service life. The diffusion of chloride ions in such an environment results in the attrition of reinforcement bars, which damages integrity, and load-bearing capacity of RC elements. Probabilistic approaches can address the uncertainty of variables associated with chloride ingress in an RC element to develop feasible solutions. This study investigates the impact of a few uncertain parameters viz., (i) chloride concentration \(({C}_{s})\) , (ii) cover depth in concrete \(\left(D\right)\) and (iii) diffusion coefficient \({(D}_{c})\) , on the chloride ingress using the Finite Element COMSOL Multiphysics model coupled with reliability analysis. In this study, the probability of critical chloride concentration exceeding the value of \(19.723\text{ mol}/{m}^{3}\) ( \(0.6\text{ kg}/{m}^{3}\) ) as per IS 456:2000 code, is regarded as the failure probability \(({P}_{f})\) of RC structural element. Conversely, the reliability index \((\beta )\) represents the non-exceedance probability. The Response Surface Methodology (RSM) and linear regression analysis is adopted to obtain mathematical model for reliability analysis. The validation of the model was with Bentz et al., (2014) and the average error in the approximation was 4.5%, confirming the acceptable accuracy of the derived model. The reliability analysis revealed that the RC element could withstand the chloride concentration of up to \(60\text{ mol}/{m}^{3}\) for 50 years. In the IS 456:2000 code, the chloride content threshold may need to be revised. Furthermore, the uncertainties associated with \({C}_{s}\) and \(D\) are detrimental, while that of \({D}_{c}\) exhibited minimal impact on the reliability. In addition, 20 and 37% of cement with fly ash inclusion yielded the desired \(\beta\) of 3.0 for water to binder (w/b) ratio of 0.45 and 0.55 respectively. This study offers optimization of RC structural members for durability and assists in the maintenance and rehabilitation of marine structures.
