Infrasense recently performed a Ground Penetrating Radar (GPR) survey and analysis of 9 interstate bridge decks consisting of 3-4 lanes in each travel direction, with the goal of evaluating the approach slabs for rebar depth and asphalt concrete (AC) overlay thickness (where applicable).
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The GPR data collection was carried out using a vehicle-based dual 1-GHz horn antenna system. Also equipped was an electronic distance-measuring instrument (DMI) mounted to the rear wheel, providing synchronous distance data with the GPR collection. A GPS unit provided high resolution, differentially corrected geo-spatial information. An SIR-30 GPR system, operated from within the survey vehicle, controlled data collection and recording. The data was collected at a rate of two scans per foot of travel along each surveyed lane.
Analysis of the GPR data included tracking the upper rebar layer in all slabs and reporting the thickness of the concrete cover. The majority of the 18 slabs had asphalt overlays that were also analyzed and reported for thickness. Due to many instances of structural inconsistency occurring laterally across a single slab, the AC overlay and Portland Cement Concrete (PCC) rebar cover measurements were broken down into groups based on lateral offset. Individual slab layers were “picked” by an analyst, with a software carrying out the dielectric and thickness calculations on the picked data. Layer thicknesses were calculated and reported at one-foot increments along each surveyed lane of each approach and departure slab. These values were used to calculate the average, median, standard deviation, and 25th and 75th percentiles of the concrete cover and asphalt overlay (as applicable) for all 18 approach and departure slabs.
The GPR data collected for each of the 9 surveyed bridge decks was analyzed for concrete cover and AC overlay thickness, with results presented in tabular format.
About Infrasense, Inc.
Since 1987, Infrasense, Inc. has applied advanced technologies to address the most difficult challenges in subsurface scanning. Infrasense's engineers nondestructively extract critical information from a diverse range of structures. In addition to providing ongoing subsurface evaluation services to clients across the country, the firm has also conducted numerous research programs to advance the field of subsurface detection and nondestructive evaluation. To learn more about Infrasense and the services we provide, visit our website: http://www.infrasense.com.
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SOURCE Infrasense, Inc.
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