Background
Traditionally, removing ice from pavement can be accomplished by a combination of several methods, such as plowing, natural melting, traffic movement, and chemical treatment. Because the bond between ice and pavement is strong, removal by plowing alone is not effective. Chemical treatment helps break the bond by melting into the ice and spreading under the ice layer. Most highway winter maintenance depends on using chemicals and fine granular particles as a primary means for deicing. However, using deicing chemicals and salt has caused damage to concrete and corrosion of reinforcing bars in concrete bridge decks which is partially responsible for the rapid deterioration of the transportation infrastructure in the U.S. The search for improved deicing methods has been a research focus for quite some time. The use of electric heating cables and heated fluid in pipes have been attempted, however, those techniques were too expensive to operate and difficult to maintain.
Conductive concrete is produced by adding electrically conductive components to a regular concrete mix to attain stable electrical conductivity. Due to its electrical resistance, a thin layer of conductive concrete can generate enough heat to prevent ice formation on concrete pavement when connected to an AC power. Under a research sponsored by Nebraska Department of Roads, a concrete mix containing 1.5 percent of steel fibers and 25 percent of steel shavings was developed specifically for concrete bridge deck deicing. The mix has adequate strength and provides a thermal power density of 590 W/m2, producing a heating rate of 0.56oC/min under subfreezing temperature. The average energy cost was about $0.8/m2 per snow storm. A comparison of conductive concrete technology against other deicing technologies in the literature has revealed that it has the potential to become the most cost-effective deicing technology in the future.
The benefits from this project will demonstrate that the project has national and international importance. Statistics indicate that 10 to 15 percent of all roadway accidents are directly related to weather conditions. This percentage alone represents thousands of human injuries and deaths and millions of dollars in property damage annually. Ice accumulation on paved surfaces is not merely a concern for motorists; ice accumulation on pedestrian walkways accounts for numerous personal injuries, due to slipping and falling. The payoff potential for this project is tremendous: it would eliminate icy bridge roads for wintry travel safety and save lives. The conductive concrete deicing technology is readily available for implementation at accident-prone areas such as bridge overpasses, exit ramps, airport runways, street intersections, sidewalks, and driveways.
The findings of our conductive concrete research showed that using thin conductive concrete overlay could become the most cost-effective bridge deck deicing method. Nebraska Department of Roads has initiated a demonstration project at Roca, located about 15 miles south of Lincoln, Nebraska, to implement a conductive concrete overlay on a highway bridge. The Roca Spur Bridge has a 46 m long and 11 m wide conductive concrete deck overlay. A railroad crossing is located immediately following the end of the bridge, making it a prime candidate for deicing application. The Roca Bridge project was let in December 2001 and construction began in the summer of 2002. The overlay is being instrumented with temperature sensors to provide data for heating performance monitoring during the winter of 2002.