In-suit monitoring electrical resistiviy in cover-zone concrete by Tower Type Sensor

Tower Type Sensor (TTS) system was developed to monitor depth-related electrical resistivity in chloride-contaminated concrete. The AC impedance method was adopted to measure the electrical resistivity of concrete. This paper also details arrangements of TTS and its calibration approach. Then the sensor geometric constant k was determined by 0.01 mol/L KCl solution. In view of the RC circuit characteristics of concrete, a frequency range from 50,000 Hz to 100 Hz is preferable to traditional constant frequency, and the latter is found to be less accurate in concrete due to influence of interface capacitance. All the studies demonstrate that TTS could serve as a part of early warning system in cover-zone concrete.