TRIAL APPLICATION OF ELECTROCHEMICAL CHLORIDE EXTRACTION ON CONCRETE BRIDGE COMPONENTS IN VIRGINIA

Electrochemical chloride extraction is a new technique for mitigating chloride-induced corrosion of the reinforcing bars in concrete bridges. To demonstrate the feasibility of applying this technique on full-sized concrete bridge members and to identify needed improvements to the technology, the technique was tried on two concrete deck spans and three concrete piers in Virginia. For the two deck spans, an anode system consisting of felt-sandwiched catalyzed titanium mesh kept wet by an electrolyte was used. An electrical charge of 741 to 1077 A-hr/sq m was applied between the anode and the steel bar for 57 or 58 days. Approximately 72 to 82% of the chloride ions was removed from the concrete at the depth of the first mat of steel bars. For the three piers, an anode system consisting of wet cellulose fibers and steel or titanium mesh was used. An electrical charge of 249 to 382 A-hr/sq m was applied between the anode and the steel bars for 72 to 77 days. The system for the piers appeared to be relatively less effective than that for the deck spans, removing approximately 13 to 53% of the chloride ions from the concrete near the steel bars. In addition, more problems were encountered with this treatment system. No damage to the concrete attributable to the treatment was observed with either system, and it is likely that shorter treatment times would have sufficed. Based on potential surveys, the bars in the concrete piers were still passive at 4 years after treatment. To facilitate the comparison between electrochemical chloride extraction and other corrosion control options, such as impressed-current and galvanic cathodic protection, preliminary information on the costs and projected service lives of all options is provided.