Empirical Investigation of Concrete Durability Indicators for Infrastructure in the Niger Delta Coastal Environment

Reinforced concrete infrastructure in the Niger Delta coastal environment degrades at rates significantly above design assumptions due to combined chloride ingress, carbonation, hydrocarbon contamination, and biological fouling, yet empirical durability data specific to this environment are limited. This study empirically investigates concrete durability through analysis of infrastructure in service across the Niger Delta coastal zone. A cross-sectional empirical investigation examined 52 concrete infrastructure elements (bridge piers, quay walls, jetty piles, and building columns) in coastal Rivers, Bayelsa, and Delta States, stratified by exposure zone (tidal, splash, and atmospheric) and age category. Durability indicators tested include chloride content profile by depth, carbonation depth, half-cell potential, concrete resistivity, compressive strength, and cover depth. Probabilistic models for chloride-induced corrosion initiation time were calibrated using the empirical data. Results indicate that chloride-induced reinforcement corrosion has initiated in 78 percent of elements over 15 years old in tidal zones and 45 percent of elements in splash zones. Mean concrete cover is 28 mm, significantly below the recommended 50 mm minimum for XS3 exposure. The empirical chloride diffusion coefficients (Dc = 1.4 to 3.2 x 10-12 m2/s) are 40 to 65 percent higher than values used in current design guidance, indicating faster-than-assumed deterioration. The study provides calibrated durability parameters for Niger Delta coastal concrete design.

Keywords: concrete durability, chloride ingress, Niger Delta, coastal infrastructure, reinforcement corrosion