Early Detection of Corrosion Damage in Reinforced Concrete Using GPR Array Imaging Method

Corrosion of reinforcing bars constitutes a significant factor contributing to cracking and spalling in reinforced concrete (RC) structures. To prolong the service life of RC structures, it is crucial to develop a robust nondestructive inspection system for early-stage corrosion damage assessment. Although ground-penetrating radar (GPR) has proven its effectiveness in detecting severe corrosion damage, identifying early-stage corrosion with conventional GPR methods with single-input-single-output (SISO) configuration is challenging due to their limited sensitivity to subtle changes in the properties of the reinforcing bar and the surrounding environment. To address this challenge, this study introduces a method that employs a GPR array to increase sensitivity in detecting early-stage corrosion. The method uses a linear multiple-input-multiple-output (MIMO) GPR array to reconstruct images of the reinforcing bars during the corrosion process. The reconstructed images are highly sensitive to corrosion-induced rusts and cracks that exhibit different dielectric permittivity and conductivity compared to the concrete. By analyzing the differences in these images from those of bars in a healthy state using the structural similarity (SSIM) index, the progression of corrosion can be precisely identified. The effectiveness of this method has been validated through numerical simulations and experimental corrosion monitoring tests. Compared to conventional SISO GPR configurations, the MIMO array offers a broader perspective in sensing corrosion products surrounding the reinforcing bars, thereby improving sensitivity and robustness in detecting early-stage corrosion.