Infrasense and BDI mobilized to Norfolk, Virginia to complete testing on the 1800-foot long bridge deck. The methods of testing included GPR, HCP, coring, and chloride sampling. Testing was performed in September on 14 select panels of the bridge deck, with the goal of identifying rebar depth and spacing, and areas of probable corrosion.
The GPR data was collected using a 1.5 GHz ground-coupled antenna system, manufactured by GSSI in the United States. Once field work was completed, experienced analysts took the data and produced three-dimensional renderings of the upper and lower mats of rebar for all 14 bridge deck panels.
The resulting GPR data showed a cross-sectional slice of the bridge deck at various offsets. Each slice included layers of the top and bottom of the deck, as well as the top and bottom mats of reinforcing steel.
The resulting GPR data showed a cross-sectional slice of the bridge deck at various offsets. Each slice included layers of the top and bottom of the deck, as well as the top and bottom mats of reinforcing steel. The amplitudes of these layers were calculated and then quantities and maps of concrete cover were produced. The maps were provided in both PDF and CADD compatible formats. The resulting quantities included rebar depth and spacing statistics for each panel.
The Half Cell Potential (HCP) measurements were carried out according to ASTM C876-91 on a 5-ft by 5-ft grid within each of the testing sections. Cores were taken to access the rebar and make electrical contact, and then repurposed for the use of chloride sampling, minimizing the number of total cores taken. The results included maps of corrosion probability for each panel.