||Anti-Ice Coating Passes Test
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|APRIL 10 -- There's a bridge along Wisconsin's Highway 8 |
that's notorious for ice and bad wrecks. But this
winter, no one has spun out and slammed into the
guardrails above the Wolf River, and officials
say that's no accident.
Last summer, workers installed a new surface on
the 120-foot span, located about six miles west
of the small town of Crandon, Wis. Developed by a
researcher at Michigan Tech, this anti-icing
pavement overlay is a sheet of epoxy covered with
an aggregate. From the top, it looks like kitty
litter. A cross section looks more like toffee
covered with lots of chopped nuts.
"It acts sort of like a hard sponge," says
inventor Russ Alger, a project manager/research
leader at the Keweenaw Research Center. "You put
a light amount of de-icing chemical on there, and
it keeps coming up to the surface."
Thus, when salt trucks apply magnesium chloride
to the bridge, it doesn't just sit on top of the
concrete, to be pushed off by snow plows or
washed into the river. It soaks into the overlay
and stays put.
This can save money. "You don't have to use very
much chemical, and you don't have to apply it
very often," Alger says.
When the time came to test the overlay, Alger
approached the Wisconsin Department of
Transportation, which has no shortage of
treacherous roadways, especially in the north.
"They told me, 'We're going to give you the worst
bridge in the state,'" Alger recalls. "It had the
highest accident rate and the worst frost and
The bridge crosses a river that gives off a lot
of steam, which condenses and freezes on the
pavement. Plus, it's midway up a steep hill.
Motorists come barreling up Wolf River Hill with
their cruise control set on 60 mph. "If you are
accelerating and your tires hit that ice, you are
off to the races," observes Ron Cole, patrol
superintendent of the Forest County Highway
As a result, Cole has received more than one 3
a.m. call from state police asking him to send a
salt truck out to the bridge, which has seen five
accidents in the past two years.
However, with the anti-icing overlay coating the
pavement, his phone has been quiet. There have
been no accidents so far this winter, and crews
have applied magnesium chloride to the bridge
only five times, fewer than half the typical
"One time I was out there, and the bridge was
white on both sides and wet in the middle," Cole
said. "It's been a success in my mind."
Alger hopes that the Wolf River Bridge success
will be repeated elsewhere. Michigan Tech is
negotiating a licensing agreement with a large
corporation to use the anti-icing pavement
overlay, and plans are under way to install it
this summer on a number of accident-prone sites
across the Midwest.
If the Wolf River Bridge trial is any indication,
highway departments will see the cost of treating
their trouble spots plummet, and drivers will
make fewer trips to the body shop--and to the