Evaluation of Electrochemical Chloride Extraction (ECE) and Fiber Reinforced Polymer (FRP) Wrap Technology

In this project, researchers investigated methods for mitigating corrosion in reinforced concrete structures on the substructure of a bridge in Minneapolis, Minn. They treated several corrosion-damaged columns and pier caps with electrochemical chloride extraction (ECE). Then selected ECE-treated and untreated structures were wrapped with FRP wraps or sealed with concrete sealers to prevent future chloride ingression. They installed embeddable corrosion monitoring instrumentation in the field structures to evaluate the effectiveness of ECE treatment. Although the ECE process reduced average chloride levels in the treated structures by approximately 50 percent, several locations still had chloride concentrations in excess of the established corrosion threshold following ECE treatment. Resistivity probe failures that occurred at some of these locations indicated corrosion within the treated structures still could occur, despite re-passivation of the reinforcing steel following ECE treatment. Continued monitoring of the installed instrumentation is required to evaluate the long-term effectiveness of ECE treatment and concrete wrapping/sealing as a corrosion mitigation technique. In laboratory testing of the three FRP wrap types, the Mbrace CFRP and GFRP reported higher peeling loads and lower diffusion rates than the AMOCO CFRP, and thus were considered more effective sealant systems. However, concrete sealers are recommended to prevent future chloride ion ingress, instead of FRP wraps, because the use of sealers does not prevent visual insnection of the concrete for corrosion damage.