In 2004, the Illinois Department of Transportation (IDOT) and the Federal Highway Administration (FHWA) completed the 2003 IDOT/FHWA Joint Process Review on Bridge Parapet Construction, aimed at evaluating the adequacy and long-term performance of concrete barriers constructed as bridge barriers and roadway dividers. The review identified widespread deterioration and serviceability-related performance issues with slip formed barriers compared with barriers constructed using conventional cast-in-place methods. At the request of the Bureau of Bridges and Structures of IDOT, the Bridge Maintenance and Inspection Unit of the Iowa Department of Transportation and the FHWA, the project team completed a multi-phase research study aimed at identifying costeffective, nondestructive evaluation (NDE) methodologies that may be effective in 1) identifying internal defects within slip formed concrete barriers and 2) assessing the corrosion condition of barrier dowel bars. Nondestructive testing methods to assess production-related flaws included impact-echo ultrasonic, shear wave ultrasonic tomography, ultrasonic pulse velocity, ground-penetrating radar, infrared thermography, and radiography testing. Nondestructive testing methods to assess corrosion-related distress included half-cell potential surveying, corrosion rate measurement, impulse-response structural mobility testing, and concrete resistivity measurements. To evaluate the effectiveness of each NDE technique, this study combined laboratory testing of mock-up bridge deck and barrier wall samples with known defects and field testing of barrier walls on in-service bridges in Iowa and Illinois. Each NDE technique was judged on its capabilities with respect to internal flaw detection and dowel bar corrosion, respectively. Results of the assessment were compiled in a comprehensive research report which included guidelines for the selection and practical application of specific NDE methods for evaluating in-place barriers.
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