Pilot applications of electrochemical chloride extraction on concrete piers in Virginia.

Applying a temporary electric field between the concrete surface and the rebars can expel or remove chloride ions from salt-contaminated reinforced concrete, which will mitigate rebar corrosion. A new method for the permanent rehabilitation of concrete bridges, based on the technique of electrochemical chloride extraction (ECE), was applied to three concrete piers as part of pilot trials in Virginia, to demonstrate the practicality of the method on full-sized bridge elements and refine implementation techniques. The ECE treatment involved placing a simple wet mesh-and-fiber anode system on the surface of the piers. A total electrical charge of 249 to 382 A-hr/sq m (23.1 to 35.5 A-hr/sq ft) was applied between the anode and the rebars underneath a total of 488 sq m (5,253 sq ft) of concrete for 72 to 77 days (a shorter treatment time would likely suffice). Approximately 27.2 to 59.9% and 12.9 to 52.7% of the initial chloride ions were removed from concrete at the depths of 0.6 to 1.9 cm (0.25 to 0.75 in.) and 2.5 to 3.8 cm (1.0 to 1.5 in.), respectively. Some problems with the system were encountered during the treatment. All the problems were correctable. No discernible adverse effect on the concrete due to the treatment was observed. The project demonstrated that ECE treatment of full-sized concrete bridge piers can be conducted with reasonable success.