Rebar characterization using dual-polarization GPR

Ground-penetrating radar (GPR) has been extensively employed for inspecting reinforcing bars (rebars) in concrete. Although traditional single-channel GPR can efficiently detect rebar and determine its cover thickness, it is of difficulty to accurately estimate rebar diameter due to its limited resolution. Through calculating the analytical solutions of electromagnetic scattering signals from a metallic cylinder in two orthogonally-polarized channels, this paper proves that their phase difference is sensitive to the cylinder's diameter. Consequently, a method is proposed for estimating rebar diameter from the phase difference measured by a dual-polarization GPR system. The effectiveness of this method is validated through numerical, laboratory, and field experiments. The results indicate that a high accuracy with errors less than 1.3 mm (9.1 %) has been achieved for rebar diameter estimation in various scenarios. Thus, it is concluded that the proposed method offers a practical solution for simultaneous estimation of rebar diameter and cover thickness in reinforced concrete structures using dual-polarization GPR.