Examples Demonstrating Identification of Rebar and Voids in Concrete Using GPR
Fig. 1. 1600 MHz GPR profile showing rebar mat inside a concrete slab. The steel rods are perpendicular to the profile and located at the apices of the diffraction hyperbolas. Top and bottom of rebar mat layer are offset. The horizontal black-white-black band represents the contact between the bottom of the concrete slab and air.*
Fig. 2. 900 MHz GPR profile of concrete slab. Diffraction hyperbolas represent rebar oriented perpendicular to the profile and located at apices of hyperbolas. White-black-white band in the lower right of the radargram represents a void in the concrete slab.*
Fig. 3. 3D GPR radargram of rebar mat showing horizontal slice several inches below surface collected with 1600 MHz antenna. To construct this 3D radargram requires collection of GPR profiles along a grid of closely spaced transects. *
* Geophysical Survey Systems, Inc., 2015b, Concrete Handbook: GPR Inspection of Concrete.