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Daytona Beach


Civil Engineering

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The use of fiber-reinforced polymer (FRP) composites to strengthen existing civil infrastructure is expanding rapidly. Many FRP systems used to strengthen reinforced concrete are applied using a wet lay-up method in which dry fibers are saturated on site and then applied to the surface. This research investigated using infrared thermography (IRT) as a nondestructive evaluation (NDE) tool for detecting air voids and epoxy-filled holes in FRP systems bonded to a concrete substrate. Four small-scale specimens with FRP thicknesses ranging from 1 to 4 mm (0.04 to 0.16 in.) containing fabricated defects were constructed and inspected in a laboratory setting. Three heating methods (flash, scan, and long pulse) were employed and a quantitative analysis of resulting IRT data was used to establish detection limits for each method. Scan heating was shown to be most effective for basic defect detection. Air-filled defects at the FRP/concrete interface as small as 2.9 cm2 (0.45 in.2) were detected in a 4 mm (0.16 in.) thick FRP system. Defects as small as 0.3 cm2 (0.05 in.2) were detected in a 1 mm (0.04 in.) thick FRP system.

Publication Title

ACI Materials Journal


American Concrete Institute

Additional Information

Title no. 104-M53

Dr. Jeff Brown was not affiliated with Embry-Riddle Aeronautical University at the time this paper was published.