Reliability Analysis of Infrared Thermography (IRT) for the Detection of Subsurface Delamination

The detection of subsurface damage using Infrared Thermography (IRT) typically relies on a subjective assessment of a color-coded image representing the surface temperature of the concrete. The accuracy of the technique may be analyzed by comparison with cores extracted from the test object in areas where subsurface damage is detected in the IR image. Assessing the accuracy in this way may be of limited utility if it is not accompanied with an assessment of the false positive rate (FPR) and the false negative rate (FNR). This paper presents an analysis method to quantitatively interpret IRT data and objectively assess its reliability for the detection of subsurface delamination, considering all correct and incorrect output. Receiver operating characteristics (ROC) in conjunction with a simplified image processing method were used to accomplish the objective of the research. Results of the study have demonstrated the capability of IRT technology to discern delaminated and sound concrete based on testing of simulated delamination. This conclusion was reached since the nonparametric estimate of the area under the ROC curve (AUC) and its 95% confidence limits were 0.867 and 0.842∼0.884, respectively.


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