Infrasense, Inc., a national leader in infrastructure nondestructive evaluations, recently completed ground penetrating radar surveys of 28 bridge decks in Ohio. These bridges represent nearly 131,000 square feet throughout the northwest section of the state. The ground penetrating radar surveys were carried out at driving speeds, so no closures were required and traffic flow was not disrupted. The GPR surveys provide a deterioration quantity and map for each reinforced concrete bridge deck and the approach slabs. Additionally, visual inspections of the deck undersides and high-resolution video surveys of the wearing surface conditions were completed for each deck. ODOT's Planning and Engineering Division will utilize the deck condition results to prioritize future preservation, maintenance, rehabilitation, and deck replacement funding.
Ground penetrating radar (GPR) data is collected at highway speeds to estimate rebar depth, corrosion conditions and deteriorated concrete. The GPR data is collected in a series of lines spaced 3 feet transversely across the width of the deck, with each line representing a cross sectional slice of the deck at a particular offset. Decks in good condition consist of strong and uniform radar reflections from the rebar. GPR data with weak and inconsistent reflections indicate rebar-level deterioration in the bridge deck. Infrasense uses software to analyze and map this data to provide comprehensive results for its clients.
Ground penetrating radar surveys provide transportation agencies with accurate and comprehensive bridge deck condition information, enabling effective preservation, rehabilitation, and replacement decisions. Traditionally, highway agencies have employed sounding (chain or hammer) to identify delaminated areas for project-level rehab. Although sounding has proven reliable, the labor and closures required for a sounding survey makes it prohibitive for obtaining data of a large number of decks. Also, sounding is not effective when there is an asphalt overlay. In response to these limitations, a number of highway agencies, including ODOT, have utilized alternative methods such as ground penetrating radar.