ABSTRACT
Infrared thermography (IRT) has become an important non-destructive testing method for the layering of concrete bridge decks. One of the obstacles to making full use of infrared thermal imaging for detection in practice is the misjudgment of thermal images caused by the non-uniformity of bridge surface conditions (such as chromatic aberration) and the presence of foreign substances on the bridge deck surface. This “noise information” not only affects the data processing of infrared thermography detection but also changes the heat conduction process of the concrete deck under the solar heating cycle, which is a key factor in stimulating the thermal contrast of infrared thermography detection. In this paper, experimental studies are carried out to explore the effects of different surface conditions (bare concrete surface and painted surface of different colors) on the development of thermal contrast of concrete delamination in image inference. A simulated concrete platform with artificial delamination of the same buried depth was designed and constructed. The thermal image, heat flux and radiation intensity data of the solar natural loading environment are continuously recorded and analyzed, and the emissivity, absorption and reflectance of surface thermal radiation are revealed. The novelty of this study is that it captures two factors that influence the development of infrared thermography (IRT) sensing and delamination thermal contrast, which have rarely been reported in previous studies. On this basis, some suggestions are put forward to reduce noise and compensate for detection in thermal image processing.
