Non-Destructive Testing of FRP-Structural Systems Applied to Concrete Bridges

With the increasing application of fiber-reinforced polymer (FRP) ­structural systems to repair and strengthen concrete structures - in particular reinforced-concrete (RC) bridges - owners are faced with the issue of how to evaluate and predict the long-term performance of FRP systems applied to RC bridges. Methods to measure over time the performance of FRP-strengthened bridges are not fully developed. For a number of concrete bridges in the Republic of Macedonia strengthened with carbon FRP (CFRP) structural systems there is a need, ten years after application, to test and evaluate the performance of the CFRP-strengthened bridges by evaluating the tri-layer CFRP-epoxy-concrete bond. The bonding structure defines bridge load performance. For 19 bridges this involves testing the bond for over 14,000 linear meters of CFRP plates. While a number of non-destructive testing (NDT) methods to measure CFRP-concrete bond performance are used in the laboratory, an effective NDT method to evaluate in the field the bond condition of large quantities CFRP material applied to RC bridges is currently not available. This paper presents an NDT method using a mobile impact-echo device configured to generate an acoustic signal that identifies areas of CFRP material de-bonding from concrete bridge members. The NDT device is designed to test efficiently large areas of bonded CFRP plates. Identification of de-bonded areas of the CFRP-concrete bridge members will provide bonding structure data necessary to support the owner’s CFRP-bridge maintenance program.