Nondestructive evaluation of FRP wrapped concrete cylinders using infrared thermography and ground penetrating radar

The objectives of this research are: (a) to investigate the feasibility of using Infrared Thermography (IRT) and Ground Penetrating Radar (GPR) for detecting debonds in Fiber Reinforced Polymer (FRP) wrapped columns, and (b) to study the effect of the debonds on reduction in compressive strength of FRP wrapped columns.; All laboratory tests were conducted on concrete cylinders of size 6" x 12" (152.4 mm x 304.8 mm) in which air-filled and water-filled debonds of various sizes were inserted. Air-filled debonds were made by cutting plastic sheets into the desired sizes whereas water-filled debonds were made by injecting water in custom made polyethylene pouches. Infrared Thermography and Ground Penetrating Radar techniques were used to locate these simulated discontinuities, and the effectiveness of each technique in identifying these debonds was carefully assessed. Infrared tests were conducted with the help of ThermaCAM(TM) S60 infrared camera manufactured by FLIR Systems, and Ground Penetrating Radar tests were accomplished with a 1.5 GHz ground coupled antenna from Geophysical Survey Systems, Inc (GSSI). As a part of this research, the effect of area of debonds on the axial compressive strength of concrete columns was also studied. Two field trips were made to Moorefield, West Virginia. During these two field trips, debonds in FRP wrapped timber piles of a railroad bridge were located and evaluated through extensive inspection.; The results reveal that a combination of Infrared Thermography and Ground Penetrating Radar can be used as an effective nondestructive evaluating tool in detection of subsurface debonds in concrete columns wrapped with Fiber Reinforced Polymer (FRP) wraps. Also, a significant decrease in axial compressive strength with an increase in area of debonds was observed.