Materials Performance

NOV 2014

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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14 NOVEMBER 2014 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 53, NO. 11 MATERIAL MATTERS Assessment tool automatically collects data on bridge deck conditions R egular monitoring and mainte- nance is required to keep the nation's ~600,000 bridges in good repair and help bridge owners to prioritize and plan rehabilita- tion projects for bridge structures. To determine the condition of their bridges, transportation agencies have relied on traditional nondestructive examination (NDE) methods (e.g., chain drag, hammer sounding, rotary percussion) to locate potential problem areas on bridge decks. Innovations in NDE technologies, how- ever, are providing inspectors with quan- titative data that are enabling them to assess the health of bridge components more quick ly and accurately. One of these innovations is the R ABIT † (Robotics Assisted Bridge Inspection areas in need of repair, which saves time and money. The technologies incorporated into the bridge deck assessment tool include a panoramic camera that collects high- quality, 360-degree images around the bridge deck as well as high-def inition cameras that capture high-resolution images of the deck surface; electrical resistivity measurement; impact echo (IE) and ultrasonic surface waves (USW); and ground penetrating radar (GPR). A ll data collected by the technologies incorpo- rated into the bridge deck assessment tool are tagged for precise location refer- ence using its high-accuracy global posi- tioning system (GPS). One major concern for bridge ow ners is corrosion of the reinforcing steel (rebar), which occurs when moisture and salt penetrate the concrete and reach the underly ing steel. As a result, the rebar starts to corrode and the resulting corro- sion products cause the concrete to crack and disintegrate. Two of the bridge deck assessment tool 's inspection technolo- gies, electrical resistiv ity measurement and GPR, help to identif y the corrosive- ness of the env ironment and its probable impact on the rebar. Electrical resistiv ity measurements determine the resistiv ity of the concrete and the rate at which steel corrosion can occur, and GPR uses electromagnetic waves to locate rebar and other metallic objects below the sur- face. High-resolution imaging prov ides v isual documentation of deck surface conditions. Another concern is the division and separation of layers of a concrete bridge deck, known as delamination, which weakens the bridge deck without outward Tool), a remotely controlled, fully auto- mated, multifunctional bridge deck assessment tool developed by the U.S. Department of Transportation's Federal Highway Administration as part of its Long-Term Bridge Performance (LTBP) program at the Turner-Fairbank Highway Research Center (McLean, Virginia), and the Center for Advanced Infrastructure and Transportation (CAIT) at Rutgers University (New Jersey). The bridge deck assessment tool incorporates an ensem- ble of the latest NDE technologies to simultaneously collect a variety of data and provide a complete assessment of the surface and subsurface of a concrete bridge deck. These data, when combined, provide an almost instantaneous, multi- dimensional portrayal of the overall con- dition of the bridge deck and help identif y The RABIT was used to assess the deck of the Arlington Memorial Bridge. Photo courtesy of Nenad Gucunski, Rutgers University. † Trade name.

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