Tracing and imaging minor water seepage of concealed PVC pipe in a reinforced concrete wall by high-frequency ground penetrating radar

This paper studies the perturbation patterns of GPR images as a tool for tracing water seepage pathway in a plastic and concealed water pipe in a full-scale concrete wall specimen. Water seepage was triggered with a water circulation system and a pre-drilled hole (as seepage point) in a PVC pipe concealed in a concrete wall. Making use of a 2 GHz antenna, different GPR perturbations patterns on the PVC pipe (as weak scatterers) and several steel bars (as strong scatterers) in concrete, were mapped. The time-lapse changes of spatial spread and degree of water seepage were monitored for 59 days to trace the water seepage path. The perturbation patterns enable the observation of the wave attenuation explained by the well-established theories of water in construction materials. Analysis in the validation experiment pushed the limit of GPR that the use of high-frequency GPR is potentially useful to trace and image minor degree of water seepage in concrete.