Corrosion of reinforcing steel is one of the major contributors to the deterioration of reinforced concrete structures. The critical element in the corrosion process is chloride ions that penetrate to the level of the reinforcing bars. One technique for dealing with this problem is the electrochemical extraction of chloride from concrete structures. This chloride extraction is accomplished by applying an anode and an electrolyte to the concrete surface and passing direct current (DC) between the anode and the reinforcing steel, which acts as a cathode. Since negatively charged ions, called anions, migrate toward the anode, it is possible to cause the negatively charged chloride ions to migrate away from the steel.

Chloride extraction is similar in principle to cathodic protection (CP) except that the magnitude of the current is 100 to 500 times that used for CP. The total amount of charge (current time) applied for chloride extraction is about the same as a CP system would deliver over a period of about 10 years. The other important difference is that chloride extraction is a shortterm treatment, whereas CP is normally intended to remain in operation for the life of the structure.

The objective of this project is to demonstrate and document the results established under the SHRP Study. A secondary objective is to work in conjunction with States, the private sector, and academia to collect data on new structures protected using the chloride extraction method. Pilot projects will include installations on both decks and substructures.

A work order with the Virginia and South Dakota Departments of Transportation to install and evaluate the electrochemical chloride extraction procedure was approved for a bridge carrying 34th Street over I-395 into Arlington, Virginia, and a bridge in Sioux City, South Dakota. The procedure was implemented on three sections of the Virginia deck and three piers of the South Dakota bridge early in the spring of 1995. The procedure was also implemented on three substructure piers on a structure in Charlottesville, Virginia, in the Spring of 1995.

Open Houses were held for the Virginia and South Dakota installations in August 1995, with ten States were represented at the Virginia Open House and five at the South Dakota Open House in Sioux City. Fifty guests, representing Federal, State, academic and private sector organizations, attended each Open House. Additional installations are now being planned in Delaware and Minnesota.

Not available.

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