Detection of Delaminations in Sunlight-Unexposed Concrete Elements of Bridges Using Infrared Thermography

Infrared thermography is a non-destructive test used in the inspection of structures. However, its use for bridge inspection is still under development and in many cases its application may be limited to bridge sections exposed to direct sunlight. This study aims to evaluate infrared thermography test for the detection of delaminations in different types of concrete not exposed directly to sunlight. The experimental methodology uses two concrete specimens with water/cement ratios (w/c) equal to 0.5 and 0.6, through the insertion of polystyrene plates of different thicknesses (3, 6 and 12 mm) and depths (25, 50 and 75 mm), in order to simulate defects within the concrete and evaluate the capacity of infrared thermography to detect them. The results show that detection is possible, but limited to short periods of time. In relation to the concrete quality, defects were more easily detected in the test specimen with lower w/c ratio. It can be said that the nearer to the surface and larger the delamination, the easier it is to detect. Also, the better the quality of the concrete, the more effective the technique becomes.