Infrared Thermography for Detecting Subsurface Defects of Concrete Structures

Delamination is one of the serious types of deterioration in reinforced concrete structures. It could cause concrete spalling, exposed steel bars, and ultimately affects the structural integrity of concrete structures. Infrared thermography (IRT) is a non-destructive technique which could potentially detect the delamination by capturing thermal contrast (∆T) on concrete surface caused by the heat flow disruption within the concrete due to subsurface anomalies. However, the optimum time and environmental conditions for IRT data collection are still unclear. In this study, an experimentally validated numerical model was developed to investigate the effect of a range of environmental conditions and defect characteristics on the IRT inspection outcomes. The results show that, under direct solar irradiation, the total heat flux input plays an important role in the development of thermal contrast ∆T instead of flux rate. Furthermore, delamination depth and size are two critical parameters that affect IRT results