Effect of the incipient anode in concrete patch repair using mortars with rice husk ash (RHA) on substrate contaminated by chlorides

Abstract

After performing localized repairs, it is customary to observe the reappearance of corrosion points in the region adjacent to the repaired area, a situation usually called the incipient anode phenomenon. Although there are several studies have on the subject, there are still controversial aspects regarding its causes, location, and progression over time. To investigate these gaps in knowledge, samples were molded with unrepaired chloride-contaminated substrate and repaired with repair mortar containing 0%, 10%, and 20% binder replacement with rice husk ash (RHA). Then, measurements of the electrochemical variables of density and corrosion potential were carried out, as well as the destructive inspection of part of the samples. After the measurements, an increase in corrosion rates was observed after the repair, in the repair-substrate interface. In the destructive inspection, significant deterioration also was observed in the repair-substrate interface region, as well as inside the substrate. Regarding the effect of replacing the binder with RHA, no relevant reduction in the incipient anode was identified in the mortars with 10% and 20% RHA. On the other hand, a possible reduction in the passivation capacity of mortar with 20% RHA content was noted.