Infrasense, a leading firm in the nondestructive evaluation (NDE) of transportation infrastructure, has successfully completed a comprehensive non-destructive testing (NDT) survey of nine interstate bridge decks. The project's primary goal was to assess the structural integrity of the bridge approach slabs by using advanced Ground Penetrating Radar (GPR) technology to determine concrete cover depth over rebar and the thickness of asphalt concrete (AC) overlays.
To achieve this, the company utilized a vehicle-based dual 1-GHz horn antenna system, ensuring high-speed and accurate data collection without the need for lane closures or disruption to traffic flow. The system was synchronized with an electronic distance-measuring instrument (DMI) and a high-resolution GPS unit to provide precise geospatial information, critical for detailed analysis and mapping. The data was collected at a high density of two scans per foot of travel, providing a rich dataset for evaluation.
The subsequent analysis of the GPR data focused on meticulously tracking the upper rebar layer to report the thickness of the concrete cover across all 18 approach and departure slabs. Given the frequent lateral inconsistencies in structural layers, measurements for both the AC overlay and Portland Cement Concrete (PCC) rebar cover were grouped based on lateral offsets, ensuring a more accurate and localized assessment. Layer thicknesses were calculated and reported at one-foot increments, and these values were used to generate a comprehensive statistical summary, including the average, median, standard deviation, and key percentiles for each slab.
The results, presented in a clear tabular format, provide infrastructure managers with a powerful, data-driven tool for making informed decisions regarding maintenance, rehabilitation, and resource allocation. This project underscores the growing importance of advanced NDT methods like GPR in the proactive management of aging transportation infrastructure, allowing for critical evaluations without compromising the safety or operational efficiency of key assets.
