Effect of penetration of water under pressure in hardened concrete on GPR signals

This paper describes the laboratory experiments carried out to analyze the effect on ground penetrating radar signals of penetration of water under pressure in hardened concrete specimens of different W/C ratio. The survey was conducted by measuring the velocities (the real permittivity) and amplitudes of the waveforms (wave energy level), recorded when the concrete specimens were first saturated, then partially dried and finally injected with pressurized water. The measurements were based on coupling a 1,6 GHz and a 2,6 GHz antennas on the surfaces of concrete specimens. The results showed that all the wave parameters studied were influenced by the presence of water in the specimens and a similar pattern behavior was observed regardless the W/C ratio. This relationship was specially highlighted by the contour maps analysis, since the spatial distribution of the studied wave parameters reproduced the shape of the injected water in the specimens. It is interesting to point out that, when measuring with both antennas after that the specimens were injected with pressurized water, we found that the wave energy level of the direct wave could be a very suitable parameter to study the depth of the water front.