Non-destructive evaluation of concrete moisture by GPR: experimental study and direct modeling

This paper reports research into the application of Ground Penetrating Radar (GPR) technology to the physical characterization of concrete and gives the details and results of an experimental study on the effect of concrete moisture on radar waves propagating through concrete laboratory slabs. Radar measurements were performed using a commercial radar system with 1.5 GHz ground-coupled antennas. The concrete slabs were conditioned so as to possess different degrees of saturation and a homogeneous moisture distribution. Electrical resistivity measurements were also carried out on each concrete sample to provide complementary information regarding the moisture content of the concrete. Interesting results were found concerning the ability of the radar technique to characterize the moisture state of concrete. Attention was especially focused on the amplitude, velocity and frequency spectrum of the waveforms recorded. In particular, the behavior of the transmitter-receiver direct wave was found to be greatly influenced by the moisture in the concrete. Finally, some experimental results were simulated using a simple dielectric model of heterogeneous mixtures. (c) 2005 RILEM. All rights reserved.