Passive infrared thermography for subsurface delamination detection in concrete infrastructure: Capabilities

Passive infrared thermography (IRT) has been introduced as a faster, safer, and contactless alternative for the nondestructive inspection of subsurface delamination in concrete infrastructure. However, some uncertainties remain, such as the absence of an inspection protocol to inspect multiple concrete components and the dependence of the technique's performance on environmental conditions and solar energy. This study presents a proof of concept about the capabilities of passive IRT in detecting subsurface damages in multiple concrete components under variate solar exposure. The passive IRT capabilities are explored by analyzing the thermal sequences obtained from samples of artificially damaged concrete structures inspected over 24 h in various environmental conditions over three seasons. As a result, damages with a size -to -depth (S/D) ratio between 1.0 and 2.7 were detected using the thermal contrast method. Furthermore, the implementation of signal processing techniques yielded an improvement in capabilities ranging from 15% to 52%. Finally, a procedure for acquiring data while inspecting multiple concrete components using passive IRT is proposed.