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• Three NDT methods with different principles to the detection of delamination. • Methods are demonstrated and validated experimentally and in-situ. • Potentials and limitations of each method are compared. Buildings, bridges, roads, and other structures need to be regularly maintained if they are to last. In general, if a defect is detected early, the cost of its remediation is typically much lower than if the structure is allowed to degrade for months or years. A key means of locating hidden defects are non-destructive testing methods. This paper describes measurements that compare three non-destructive methods applied to a concrete bridge and a laboratory specimen with artificial defects to simulate cavities. Three methods (infrared thermography, ground-penetrating radar and ultrasonic pulse echo) were used to measure the depth and size of cavities in the concrete panel. Furthermore, the measurements were made using two different brands of radar and two different thermal imaging cameras from the same manufacturer. Lastly, the NDT methods were compared across general performance criteria in terms of accuracy, testing practicality, and costs. [ABSTRACT FROM AUTHOR]