Remote sensing of air blisters in concrete?FRP bond layer using IR thermography

Studies have been conducted to: (a) detect artificially induced blisters in the bond-line between FRP components and the RC beams and (b) evaluate the influence of air-voids on the flexural performance of FRP strengthened RC elements. The air-voids were introduced within the bond-line of the concrete elements and the reinforcing FRP. These air-voids were 2.04% and 5.29%, respectively, of the section contact area with the FRP. The blisters were identified remotely and clearly using active thermographic approach. Subsequently, the flexural RC elements were tested in four-point bending configuration and their moment–curvature behaviour was determined. It was noted that the trend variation for the levels of induced blisters was similar to the perfectly bonded beams with identical test geometry. However, due to the presence of air-voids, there appeared to be a curtailment of performance both in strength and ductility of the section as the area of blisters increased.