AN OVERVIEW OF CORROSION DAMAGE DETECTION IN STEEL BRIDGE STRANDS USING TDR

The corrosion of metallic reinforcement is a major threat to aging infrastructure. Prestressed structures such as the bridges built in the early 1950's and 1960's are showing signs of deterioration. The current corrosion detection methods for embedded or encased steel reinforcement suffer from several significant drawbacks. A nondestructive evaluation technique has been developed that is capable of determining the location and severity of corrosion of embedded or encased steel rebar and strands. This technique utilizes time domain reflectometry (TDR). By applying a sensor wire alongside of steel reinforcement (such as a prestressing strand), a transmission line is created. Physical defects of the reinforcement will change the electromagnetic properties of the line. Both analytical models and small-scale laboratory tests have shown that TDR can be effectively utilized to detect, locate and identify the extent of damage in steel reinforcement in this manner. Currently, the TDR method is being used as a permanent corrosion monitoring method for Bridge 8F, a prestressed high-performance concrete adjacent box beam bridge under construction in Fredrica, Delaware. Differential TDR measurements are used to monitor serious damage due to corrosion of the steel. Experimental results from both small-scale laboratory tests and field implementation will be reported.

Wei Liu
Grad. Res. Asst., Dept. of Electrical and Computer Engineering
University of Delaware
Newark, Delaware

Robert G. Hunsperger
Professor, Dept. of Electrical and Computer Engineering
University of Delaware
Newark, Delaware

Michael J. Chajes
Associate Professor, Department of Civil and Environmental Engineering
University of Delaware
Newark, Delaware

Eric Kunz
Industry Representative
Elkton, Maryland