Chloride Ingress and Corrosion of Steel Bars in Reinforced Concrete Made with Different Aggregates

Abstract

Chloride-induced corrosion of reinforced concrete structures is one of the main reasons of deterioration of concrete structures in the marine exposures. A detailed investigation was carried out to compare macro-cell, micro-cell corrosion progress and chloride ingress in concrete made with different types of aggregates, such as recycled brick aggregate (RBA), fresh brick aggregate (BA) and stone aggregate (SA) as coarse aggregate. As fine aggregate natural river sand (NS) and recycled brick fine aggregate (RBFA) were used. CEM Type I (Ordinary Portland Cement (OPC)) was used as binding material. Cement contents were 340 and 400 kg/m3. W/C ratios were 0.45 and 0.55. For investigation, reinforced specimens were made. As reinforcement both deformed bars and epoxy coated bars were used for investigation. Both cracked and un-cracked specimens were investigated. A total 16 cases was investigated. The cracked prism specimens were splashed with natural seawater one in a day. Un-cracked cylindrical specimens were submerged in 3% NaCl solution of temperature 400C for 180 days. The cylindrical specimens were cut to collect concrete samples from the depths of 0-10, 10-20, 20-30, 30-40 and 40-50 mm. Chloride profiles in concrete were evaluated by titration with AgNO3 solution at 120 and 180 days of exposure. The recycled brick aggregate showed the highest level of chloride ingress compared to the other aggregates. The rate of macro-cell corrosion with respect to the type of aggregate is ordered as recycled brick aggregate (RBA) > fresh brick aggregate (BA) > stone aggregate (SA). It was also observed that chloride ingress as well as corrosion formation rate reduces with the increase of cement content and decrease of W/C ratio. No significant amount of corrosion was observed for the cases with epoxy coated bars.