Assessment of the Condition of an Existing Marine Concrete Structure in the Niger Delta Region of Nigeria

摘要

Chloride induced reinforcement corrosion is the major cause of premature deterioration of reinforced concrete structures in the chloride-laden Niger Delta region of Nigeria. This study evaluated the extent of deterioration of an existing 45 years old concrete quay structure. The methodology adopted for the study includes conducting a visual inspection on the structure to determine the current condition of the structure and the nature of testing required. Next, several non-destructive tests were carried out to determine the compressive strength, nature of corrosion and the impact on the structure. Water samples were also collected for chemical analysis, to ascertain the corrosion inducing compounds present in the surrounding seawater. The results indicated that the quay structure suffered from chloride-induced corrosion, imposed by the surrounding seawater. Measurement of the level of corrosion carried out on steel reinforcement samples obtained from the quay showed a high-level of corrosion, with rates of 0.65 uA/cm~3, evident by an average weight loss of 47% per meter length of steel. Compressive strength obtained via rebound hammer test showed average concrete strength loss of 28% from the original as-built strength of 40 N/mm~2. The results showed that the rate of corrosion and strength deterioration depended on the nature and length of exposure. Elements of the structure that were exposed to tidal exposure conditions experienced greater levels of deterioration compared to elements that were continuously submerged.