HIGH-RESOLUTION GPR BRIDGE DECK EVALUATION SURVEYS

The use of a shielded, 1.5 GHz center frequency ground-coupled di antenna has been beneficial for determining the depth of the top layer of rebar in new bridge decks and assessing the condition of concrete near the top rebar mesh in two asphalt overlaid bridge decks. The vertical and horizontal high-resolution capability of antenna yields data that contain isolated reflections from indivi rebar spaced approximately 15 cm (6in) between centers. Some DOT quality assurance-quality control (QA/QC) specifications required postconstruction inspection of new concrete bridge decks necessit determination of the average depth of the top layer of rebar and variability of the rebar depths. The 1.5 GHz antenna was investig to assess its performance for such a task. After depth calibratio the processed 1.5 GHz antenna data resulted in calculated top lay rebar depths that were accurate to within +/- 3 mm (0.12 in). Thi specific 1.5 GHz antenna design was also used to study two asphalt-overlaid bridge decks scheduled for disassembly and showe very promising results in assessing the condition of the concrete near the top rebar mesh that may lead to improved bridge deck evaluations in the near future. For the covering abstract see IT E117314.