Experimental Detection of Reinforcing Bar Corrosion Using Nondestructive Geophysical Techniques

In this study, electrical impedance and ground-penetrating radar (GPR) methods were used to indicate corrosion of steel reinforcing bars embedded in a concrete block. Corrosion of the reinforcing bars was accelerated using an anodic polarization technique. Measurements were collected using both geophysical techniques before and after the corrosion experiments. Analysis of the geophysical measurements indicated the potential benefits and limitations of the two geophysical methods for assessing reinforcing bar corrosion. GPR methods have the advantage of providing a quick indication of alterations at the interface of the reinforcing bar surface and the surrounding concrete, and they have the potential to yield very high spatial resolution information. Although the electrical impedance techniques require longer measurement times and typically have lower spatial resolution than GPR techniques, these methods have the potential to provide valuable quantitative information about the corrosion process. Indications that corrosion had occurred were obtained independently and consistently from the two geophysical methods, and the observations were also corroborated by visual examination of the reinforcing bar corrosion state via destructive analysis of the experimental block. This first study suggests that these methods hold potential for direct and early detection of reinforcing bar corrosion, and that the combined use of the two methods for assessing reinforcing bar corrosion state merits further study.