Nondestructive Evaluation of External Post-Tensioning Systems to Detect Grout Defects

Abstract

Management of bridge assets requires a life-cycle approach that balances design and construction of new bridges, and maintenance of existing bridge stock. There has been a growing need for inspection, maintenance, repair, and strengthening of existing bridge structures due to aging transportation infrastructure. Condition assessment of post-tensioning systems could allow bridge owners to take timely, proactive actions to mitigate or prevent further deterioration and unanticipated failure. An experimental study to evaluate various nondestructive evaluation (NDE) techniques for the condition assessment of grout defects in external post-tensioning systems is presented. To evaluate the NDE technologies, a full-scale post-tensioned girder specimen was constructed at the Texas A&M University RELLIS Campus. Several grout defects including voids, water infiltration, and compromised grout were fabricated and placed in the specimen for the evaluation of the NDE methods. The research team, in collaboration with several industry partners, used various NDE technologies, such as sounding, impact echo, low-frequency ultrasound, ground-penetrating radar, infrared thermography, and electrical capacitance tomography, to evaluate the grout condition of the external tendons of the post-tensioned girder specimen. Comparison of the test results with the actual defects revealed the performance of each method in detecting the location and the severity of the various grout defects in the external tendons of the post-tensioning system.