Studies on Corrosion Initiation in Reinforced Concrete Structures Using Ground-Penetrating Radar

The present article describes an example of the use of ground-penetrating radar (GPR) to detect early stages of reinforcement corrosion. Two series of concrete samples with reinforcing bars were tested. The first series was reference samples (without corrosion). Samples of the second series were subjected to accelerated corrosion by immersing them in NaCl solution, while undergoing 120 freeze-thaw cycles. Unlike the commonly used electrochemical method of corrosion acceleration, in the studies discussed here, the corrosion processes were more similar to natural ones, taking into account the influence of changes in the structure of the cover under the influence of frost. GPR scanning of samples of both series indicated that all physical and chemical processes accompanying corrosion together caused a decrease in the amplitude of the reflected wave and an increase in its propagation time. The wave amplitude, due to the significant dispersion of results, was, however, a rather unreliable parameter. The wave propagation time was characterized by significantly better repeatability, which makes it a better measure of the progress of corrosion. In general, the GPR with a 2 GHz antenna proved to be an effective tool for diagnosing early stages of corrosion in reinforced concrete.