Investigation of the applicability of infrared thermography detection of grouting voids in prestressed tendon ducts under hydration heat excitation

Infrared thermography (IRT) has been successfully utilized to identify void defects in external prestressed tendon ducts (without concrete protective layers) under hydration heat excitation. Nonetheless, applying IRT technology for the inspection of internal prestressed tendon ducts presents challenges due to the presence of the thicker concrete protective layer, which can significantly influence the detection results. Therefore, this paper proposes a method for detecting void defects in internal prestressed tendon ducts using IRT technology under hydration heat excitation. The influence of the depth, length and compactness of the void on the detection ability is investigated and the influencing factors such as duct materials are analyzed. The results show that under the hydration heat excitation of the grouting material, IRT can detect complete void defects with a depth of 110 mm below and a length of 350 mm. In addition, the detection effects of metal ducts, tubeless ducts and plastic ducts decrease in turn. Finally, this paper recommends that the IRT detection time be 0.5–2 h and 13–23 h after grouting, which can reduce the cost of post-maintenance by timely detection and repair.