Non-destructive Inspection of Chloride Ion in Concrete Structures Using Attenuated Total Reflection of Millimeter Waves

The chloride induced corrosion of reinforcing steel bar is one of the major causes of deterioration of concrete structures. Therefore, it is essential to periodically monitor the level of chloride ion (Cl^-) concentration in concrete structures. In this work, we developed millimeter wave attenuated total reflection measurement setup in order to determine the Cl^- concentration in concrete structures. We prepared concrete samples with different compositions and varying Cl^- concentrations and we measured their attenuated total reflectance at 65 GHz. We observed that the reflectance decreases almost linearly with the increase in Cl^- concentration indicating that this technique could be used to inspect the Cl^- concentration in concrete structures nondestructively.