Ground Penetrating Radar wave behavior under different corrosion levels of concrete

Corrosion of reinforced concrete structures is the most significant issue for its safety and lifetime. During the structural assessment of lifetime evaluation of structures, destructive tests might increase the damage size of the structure. This investigation attempts to identify the corrosion effect of the reinforcement in concrete and chloride contamination of the concrete using Ground Penetrating Radar (GPR) as a non-destructive testing method. A 300 mm wide, 600 mm long and 100 mm high three concrete slab panels were prepared using a 12 mm rebar. After 28 days of casting the concrete slab panels, reflection and common mid-point GPR surveys were performed using Pulse EKKO PRO system with 1000 MHz centre frequency transducers. The concrete panels were partly submerged in 5% NaCl solution and reinforcement bar was corroded using the impedance current technique. A 17.2 V DC current was applied to accelerate the corrosion of slab panels and kept it for 24 hours. The GPR surveys were repeated and the same procedure was performed after 48 h, 72 h and 96 h of submerged time intervals. With parallel to each GPR data acquisition steps, half-cell potential test was also conducted. The collected GPR data were analyzed separately using the EKKO Mapper, GFP Edit and EKKO View Deluxe software packages. Analyzed results clearly showed that the GPR wave velocity did not change with corrosion time, but the reflected wave amplitude decreases with increasing corrosion time which is in correspondence with the half-cell potential test.