Effectiveness of CNI in slabs with a construction joint in a marine environment

In marine concrete structures, construction joints, formed at the intersect of the end of one concrete placement and the beginning of a new placement, have been identified as vulnerable zones that may permit the intrusion of chlorides over a relatively small area of the reinforcement, thus accelerating corrosion. The present paper reports a research study to evaluate the effectiveness of calcium-nitrite corrosion inhibitor in combination with pulverised fly ash on the corrosion protection of reinforced concrete slabs manufactured with a construction joint intersecting the reinforcement at right angles and exposed to a marine environment for seven years. Electrochemical testing, chloride profiling using the scanning electron microscope/energy dispersive X-ray analyser and assessment of the damage caused by chloride-induced corrosion on the reinforcing bars, were conducted. Results showed that bars retrieved from low water/cementitious material ratio concretes containing calcium nitrite and fly ash experienced negligible corrosion damage; conversely, in specimens prepared with high water/cementitious material ratio, this combination provided a low level of protection.