Unique aggregate absorbs chemicals for continued release during storms
This winter and next, researchers at the Virginia Transportation Research Council (VTRC) will evaluate a new bridge overlay that is capable of reducing ice buildup on bridge driving surfaces.
The overlay's 3/8-inch-thick layer of aggregate can absorb, store and slowly release through several snow storms deicing chemicals that are expected to decrease ice buildup on a bridge surface. Such surface materials, also known as epoxy overlays, generally extend the life of bridge decks; however, this specific aggregate-chemical combination has the potential to minimize snow and ice-related crashes on bridges as well
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Contract workers apply a special epoxy overlay to a bridge deck on I-81 in Staunton District. This overlay contains an aggregate that slowly releases deicing brine that can reduce ice buildup on bridge surfaces. The VTRC is studying the overlay.
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The innovative limestone aggregate allows commonly used salt-brine deicing solution to "penetrate the pores of the aggregate like a sponge," according to Michael Sprinkel, materials associate director at VTRC, who is overseeing the project. Standard epoxy bridge overlays consist of a silica-basalt aggregate, which does not have the absorption capabilities of this limestone aggregate.
The aggregate, originally developed by Michigan Technological University's Keweenaw Research Center, also can hold enough deicing brine so it does not have to be reapplied after each winter storm; thus saving time and money as it is slowly released over time. On a Wisconsin bridge where the deicing technology has been applied, no crashes have occurred in two years
Epoxy overlays extend the life of bridge decks by minimizing water seepage and corrosion agents such as chlorides into the decks. They also improve skid resistance and the bridge's surface appearance. The overlays consist of two layers of epoxy and aggregate spread on a dry, shot-blasted surface. Besides being a low-cost, lightweight protective surface, they usually can handle traffic three hours after application and can provide a service life of 15 to 25 years
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| Michael Sprinkel, VTRC Associate Director for Materials |
Test locations for the product are on I-81 bridges at mile markers 219 and 239 in Augusta and Rockingham counties, respectively. VDOT installed the overlays in September and October.
Based on the amount of pavement surface to be covered with the new aggregate and the labor involved, the average cost of applying this product is about 30 percent more than standard epoxy overlays. However, this does not factor in the reduced costs of fewer applications of the deicing chemicals.
Cargill, the company that licensed the deicing product from Michigan Tech, has successfully tested the product on bridges in the upper Midwest. It has ongoing test sites in other Southern states as well as Virginia, and also in Northeastern states, through state transportation departments.
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