Probing Concrete with Radio Waves

Electromagnetic probing can be used to assess the integrity of concrete cofferdam seals. Data are taken using high-frequency transmitter and receiver antennas installed in separate boreholes drilled in the concrete seal, and the spatial variation of signal attenuation rate is calculated using tomographic techniques applied to the concrete structure. The results map the variation of signal attenuation rate within a plane bounded by the boreholes. Experimental results using this technique on an actual cofferdam seal show anomalous regions in the concrete. One core sample confirmed this prediction for one signal profile, but a core sample in a different region did not correlate with the profile of that region. The change in electrical conductivity of concrete with time might have caused this disagreement.