NDT Methods for Evaluating FRP-Concrete Bond Performance

The long-term bond performance, 15+ years, of FRP-structural systems applied to reinforced-concrete structures is largely unknown and not widely tested. FRP-structural system performance is a function of FRP-concrete bond condition and is subject to deterioration over time. The purpose of this investigation is to test and validate the non-destructive testing impulse-excitation technique to evaluate bond condition of FRP systems applied to concrete structures, in particular concrete highway bridges. The objective is to identify changes in the FRP-concrete bond state by analyzing changes in impulse excitation (impact) frequencies and sinusoid waveforms. Hammer impact tests were performed on two FRP-retrofitted highway bridges in Missouri and a bonded FRP test plate in the laboratory. Signal analysis of recorded impact acoustic emissions was performed on frequencies and waveform damping ratios of bonded and de-bonded FRP material on two bridges and in the lab. The frequencies and sinusoidal waveforms of the bonded and de-bonded FRP material on the bridges had a high degree of correlation to those of the bonded/de-bonded laboratory FRP plate. This investigation confirms the impulse excitation technique to test FRP bond on concrete structures, which provides accurate data on the bonded versus de-bonded FRP-bond condition