Evaluating the Long-Term Durability of Externally Bonded FRP via Field Assessments

Abstract

Fiber-reinforced polymer composites (FRP) are an attractive repair option for reinforced concrete structures, but whereas laboratory durability tests have indicated that FRP generally performs well in many environments, their long-term performance in field environments is not well understood. This case study describes an effort to collect in situ data about the FRP used to repair a concrete arch bridge 8 years after the FRP was originally placed. On-site assessment efforts included inspection for voids between the concrete and FRP using acoustic sounding and thermographic imaging and pull-off tests to check the bond strength. Large debonded regions of FRP were also cut from the structure and tested in tension in the laboratory. Results generally pointed to some level deterioration. Many new voids were found, existing voids had grown, pull-off testing showed weaker bond strengths, and the tensile strengths were quite low compared to design values. However, a lack of initial data make it difficult to distinguish between deterioration over time and the possibility of lower strengths because of field manufacture techniques.