Reducing Chloride Induced Corrosion Risk and Associated Life Cycle Cost of Marine RC Structure: Bangladesh Perspective

Chloride induced corrosion poses significant threat to Reinforced Concrete (RC) structures in marine environment. Therefore, proper design of marine RC structures in terms of materials types, mix proportions, and concrete cover is prerequisite for ensuring adequate durability and sustainable construction practice. Inappropriate selection of mix proportions, mix constituents, and concrete cover can significantly hamper the expected service life of a marine RC structure and eventually, results in substantial repair costs. In this study, an attempt was made to investigate the effect of binder types on corrosion risk and corresponding life cycle cost of RC slab or wall made of locally used construction materials of Bangladesh under extreme marine conditions. Five different types of binder (combinations of ordinary Portland cement and 20%/40% replacement level of slag/fly ash) and two w/b (water to binder) ratios of 0.35 and 0.45 were used along with three concrete cover values of 19 mm, 25 mm, and 37.5 mm to perform the parametric study. The Life-365 environment was used to evaluate chloride induced corrosion risk and the associated life cycle cost of RC slab or wall structure made of considered concrete mixes for a design service period of 100 years. It was evident from the study that the type of binder, use of fly ash in particular, could have considerable impact on corrosion proneness of concrete mixes. The use of a typical cover value of 19 mm for RC slabs/walls was inadequate in providing satisfactory performance under extreme saline exposure even if a higher percentage replacement of fly ash is used. The benefit of using higher concrete cover and blended cement with a higher percentage of fly ash in a saline environment was also quantitatively apparent from this study in the context of Bangladesh. Moreover, life cycle costs of marine RC structure could be significantly reduced by utilizing higher cover values and blended cement with fly ash.