Remote defect detection of FRP-bonded concrete system using acoustic-laser and imaging radar techniques

Two different remote nondestructive testing (NDT) techniques, the acoustic-laser and imaging radar techniques, are studied for near-surface defect detection in fiber-reinforced polymer (FRP) retrofitted systems. In the acoustic-laser technique, the targeted structure is excited by acoustic waves, while vibration data on a measurement point is remotely collected. In the imaging radar technique, radar signals (electromagnetic waves) are remotely emitted toward the target structure and measured when they are reflected from the structure. Three FRP-bonded concrete cylinders with various defect sizes were fabricated for laser and radar measurements. The pros and cons of these two techniques are described with the support of experimental result.