Depth Evaluation of Internal Delamination in Concrete using Infrared Thermography

In recent years, accidents resulting from spalling of concrete have been reported frequently due to the aging of concrete structures; thus, the detection of internal delamination, which is often the main factor of them, has become an important issue. Inspection technique using infrared thermography, while capable of searching over a wide region remotely without touching, still has room for improvement in terms of the accuracy of the delamination detection. In this research, a focus is placed particularly on the identification of the delamination depth. Measuring the surface temperature rise during the heating of specimens' surface with an infrared camera, a technique to identify the delamination depth is proposed based on one-dimensional non-steady heat conduction model. Experiments with mock specimens demonstrated that the evaluated delamination depths showed a good agreement with the actual ones when the heat flow can be approximated to be one-dimensional.