Factors affecting the detectability of concrete delamination in GPR images

Concrete delamination is a common type of defects in concrete bridge decks and rigid pavements. While it was reported that ground-penetrating radar (GPR) was able to visualize such types of defects in many instances, it is still unclear about the conditions of success for that application. In such a context, this study aimed to explore various factors that might affect the detectability of concrete delamination in GPR images/signals. In terms of methodology, the study was conducted using both synthetic data generated from a GPR simulation program, and real data collected on a concrete slab specimen. The analysis of such image data revealed the following. First, there is always a waveform reflected from concrete delamination. However, its strength is affected mainly by the thickness of the delamination, the material (air or water) within it, and the peak (most energetic) frequency of the emitted signal. Second, the depth of delamination and its location relative to neighboring steel bars might impact its detectability in GPR images.