Influence of antenna polarization and moisture content on detection of GFPR bars in concrete using ground penetrating radar

Glass fiber-reinforced polymer (GFRP) has recently emerged as a promising alternative to traditional steel reinforcement in concrete due to its superior durability. However, conventional non-destructive testing (NDT) methods often face limitations in detecting GFRP rebars, posing challenges for the maintenance and safety assessment of civil infrastructure. This study evaluates the applicability of ground-penetrating radar (GPR) for detecting GFRP reinforcement in concrete through both numerical simulation and experimental validation. The investigation focuses on the influence of antenna polarization and concrete moisture conditions on electromagnetic (EM) wave-based detection. Numerical simulations confirmed that increased moisture in concrete enhances dielectric contrast, thereby improving the visibility of GFRP bars. For experimental validation, two concrete specimens—a beam and a slab embedded with GFRP reinforcement—were prepared and tested. The results revealed that EM wave reflection energy increased by up to 17.0 % and 15.8 % under wet conditions using cross and normal polarizations, respectively. These findings underscore the significance of selecting appropriate antenna polarization and accounting for moisture conditions to improve the detection accuracy of GFRP rebars using GPR.