Investigation of severe corrosion observed at intersection points of steel rebar mesh in reinforced concrete construction

This paper investigates the phenomenon of high corrosion observed at many intersections of steel rebars in the wall footing of an existing reinforced concrete structure. This phenomenon is rather new and unusual and has not been reported in the past. Therefore, an experimental program was carried out to confirm the field observations and clarify the mechanism involved. Chloride-contaminated reinforced concrete panels were cast; laboratory measurements were conducted to determine the half-cell potential, corrosion current and concrete resistivity; and scanning electron microscopy and mercury intrusion porosimetry were performed. The experimental measurements at the intersection of steel rebars were found to be mostly higher than the areas between them. The high corrosion rate observed at steel intersection points appeared to be due to the coupled effects of the corrosive binding wire material, the electrical connectivity, the reduced center-to-center (c/c) steel bar spacing and poor concrete microstructure at the rebar intersection. Further detailed investigation is required for a better understanding of the effects of these factors individually.