Document Type : Research Paper
Abstract
Concrete structures in water-exposed environments are highly vulnerable to corrosion caused by chloride ingress, fluctuating water chemistry, and defective concrete cover. Corrosion damages steel reinforcement, concrete, and their bond, ultimately reducing service life and increasing maintenance expenses of structures. This study presents a non-destructive corrosion assessment of the Orogodo Composite Bridge exposed to the Orogodo River in Delta State, Nigeria. An integrated approach was adopted, combining physico-chemical water analysis with multiple non destructive evaluation methods (visual inspection, concrete cover measurement, compressive strength using a rebound hammer, ultrasonic pulse velocity-UPV, and half-cell potential-HCP) to evaluate the bridge's corrosion condition. The physico-chemical analysis classified the Orogodo River as freshwater with a chloride concentration of65.850 mg/L, indicating potential for reinforcement corrosion. Visual inspection revealed localised corrosion deterioration at section X of the bridge deck, while other RC elements and steel girders remained in visually good condition. The bridge deck's average concrete cover was approximately 75 mm, which is adequate for various exposure conditions. The average compressive strength (49.51 N/mm²) and UPV(5.57 km/s) of the bridge bottom deck indicated excellent concrete quality consistent with relevant codes and existing studies. The average HCP value of–290 mV at section X indicates a 50% probability of active corrosion, which aligns with the visual inspection findings. The findings highlight the need for adequate and defect free concrete cover, continuous monitoring, and timely maintenance of RC structures in aggressive environments. The study recommends using multiple condition assessment methods for robust evaluation of existing structures and prioritising timely repairs on the Orogodo Bridge, especially at section X, in order to prevent further deterioration and performance loss.
