Ground-probing radar has a number of applications in the investigation of concrete structures. The principal applications include estimating element thickness, determining location and cover of reinforcement, locating prestressing tendons and locating voids.
To carry out a radar survey, transmitting and receiving antennae combined in a single head are moved along the concrete surface in a series of traverses. The transmitter emits a continuous series of electromagnetic pulses. These are reflected off boundaries or discontinuities in the concrete and are picked up by the receiving antenna. The time between transmission and receipt of the signal is a measure of the distance to the surface giving rise to the reflection. The reflected energy is recorded as a pattern on paper, on a television monitor or as a digital signal. It is possible to deduce useful information from the radar patterns but it requires skill and experience. Interpretation must be undertaken by a specialist.