IR thermography for interface analysis of FRP laminates externally bonded to RC beams

Non-destructive (ND) evaluation by thermographic analysis was applied to reinforced concrete (RC) beams strengthened with CFRP laminates, to assess the quality of the interface between reinforcement and substrate before and under loading, during laboratory bending tests. The proper algorithm for processing data acquired from the thermographic system was first selected by testing reduced-scale fiber reinforced polymer (FRP)-strengthened concrete slabs with artificial defects and anomalies, deliberately placed at the interface. Portable heating equipment was purposely set-up to allow continuous scanning along the loaded beams. Results showed that infrared thermography (IRT) can supply significant qualitative and quantitative information on bonding of FRP materials applied to structural substrates, for both preliminary and in-situ investigations, by means of a reliable low-time-consuming procedure. Cross-evaluation of crack patterns during bending tests and thermographic results are also presented.