Corrosion detection of steel-reinforced concrete specimens using synthetic aperture radar

Chloride-induced corrosion attack in steel-reinforced concrete highway bridges is a common and ongoing issue in New England. If left untreated, late-stage corrosion can result in steel rebar section loss, internal stress imbalance, and surface cracks. In recent years, nondestructive testing and evaluation (NDT/E) techniques have been emerging as alternative methods for structural health monitoring (SHM) of civil infrastructure. This paper aims to use synthetic aperture radar (SAR) for corrosion detection of steel-reinforced concrete (RC) panels that were subjected to chloride-induced rebar corrosion. For this purpose, three RC panels (30x30x12.7 cm2) were cast with a No.6 steel rebar (19 mm diameter) at their mid-height with one serving as baseline, and the other two were corroded by accelerated corrosion test (ACT). The RC panels were kept in a temperature-controlled environment (23 - 25. C) since 2017. The RC panels were scanned by a laboratory 10.5 GHz SAR with a 1.5 GHz bandwidth to develop SAR images with two scan ranges of 60 and 70 centimeters. The SAR images were analyzed in time domain and their amplitude parameters were used for corrosion detection. Furthermore, a half-cell potential device was used for verification and quantification in conjunction with out SAR parameters. Our results indicate that the progression of corrosion based on HCP, is correlated with SAR signal parameters such as maximum and integrated, and average SAR amplitudes.