Effect Investigation of Delamination Shape on Detectability of Active Infrared Thermography in Painted Concrete Structures

In infrastructures, the development of defects in the core of not only normal concrete (NC) but also painted concrete (PC) structures is unavoidable. Meanwhile, the determination of the detectability of defects like delamination using non-destructive evaluation methods, i.e., active infrared thermography (IRT), has been focused much more on NC than on PC structures. Although the shape of defects varies significantly as a random variable, only square damages have been examined for PC components. This motivates the present study investigating the ability of active IRT in the detection and characterization of subsurface anomalies, i.e., delamination, with different shapes which are also then compared to those on NC structures. It is proven that the delamination shape highly affects the performance of active IRT surveys on PC structures. Particularly, the maximum absolute contrast (MAC) of square defects moderately differs from the A-shape and V-shape defects. Additionally, an A-shape defect achieves higher MAC making it more clearly observed on thermal images than the V-shape damage. Moreover, hidden defects with the same size, depth, and shape in PC components become more detectable on thermal images thanks to greater values obtained of the MAC in comparison with those in NC structures.