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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. |
