Mountain of challenges

Case Studies
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Spectacular vistas along the magnificent Blue Ridge Mountains bring thousands of visitors to Asheville, N.C., every year. Naturally, the North Carolina Department of Transportation strives to ensure the tunnels and roadways that traverse this scenic highway blend into the beautiful mountainous setting.

When the 1,050-ft-long Beau Catcher Tunnel was renovated in the winter of 1996, the DOT was faced with a mountain of challenges.

First of all, it wanted to reduce leaks and reduce the risk of rockslides.

But it also wanted to remove nearly 50 years of graffiti and accumulated dirt and residue—and keep the surface protected for years to come.

General contractor Orbit Inc. of Waynesville, N.C., knew exactly what to do. They called upon Hehr International Polymers of Decatur, Ga., to manufacture a two-component, high-performance aliphatic polyurea that utilized the latest technology from Bayer MaterialScience .

The polyurethane coating system that they recommended was developed specifically to meet the unusual conditions inside the tunnel.

When the temperature inside the tunnel rises, the substrates expand, and when the temperature drops, the substrates contract, causing the tunnel joints to move anywhere from 25 to 30%.

The polyaspartic aliphatic polyurea coating bonded to the concrete walls of the tunnel, yet offered the elasticity necessary to accommodate changing temperatures and humidity. Furthermore, it provided an anti-graffiti coating that was easy to clean and maintain.

Because the new coating system was virtually weatherproof, it kept rain, snow and wind from damaging the structure’s panels.

Every year since 1996, the tunnel has been cleaned with a high-pressure hose—a hydroseeder that effectively knocks off all the grime and debris. Then it is carefully scrutinized by a team of DOT experts trained to inspect bridge, tunnel and road surfaces for needed repairs or potential problems.

According to NCDOT’s Gary Moore, division bridge maintenance engineer, the coating system on the Beau Catcher Tunnel is living up to its expectations. “We wanted a surface that would look good and weather well,” said Moore. “The coating system on this tunnel really takes a beating every year, with all the traffic and this high-pressure cleaning. But it is holding up very well. We’d certainly use this polyurethane system again in other tunnels.”

Because of its good looks and cleanability, the polyurethane coating system on the Beau Catcher Tunnel has saved the NCDOT a considerable amount on tunnel maintenance and repair.

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