STREETS & HIGHWAYS/Midwest cities hail concrete surfacing
Over the past three years, cities in Kansas and Missouri have been using ultra-thin whitetopping (UTW) to rehabilitate high-traffic intersections. The technique’s flexibility has allowed cities to resurface severely rutted asphalt intersections, with projects ranging in size from 100 square yards to 9,000 square yards, and in depth from 2 to 4 inches.
Using the UTW technique to repair road damage, work crews first mill the damaged asphalt, leaving about 3 inches of asphalt to serve as a foundation. They then apply a thin layer of new, fiber-reinforced concrete over the damaged or distressed asphalt. The layer, typically no thicker than 4 inches, is leveled with the surrounding asphalt area.
Bob Coffman, project engineer for Topeka, Kan., uses asphalt overlays on most repair projects but employs UTW for certain types of distress and traffic loads. “Whitetopping is a viable solution for some locations with rutting problems, provided that the base and subgrade are adequate,” he says.
For example, the intersection of 30th and California streets in Topeka was badly in need of repairs. Although the spot is in a residential area, buses and garbage trucks traveled it regularly. “[The intersection features] a horizontal curve on a moderate grade, and acceleration/deceleration and turning of the buses resulted in heavy rutting,” Coffman says.
Permanent Paving, Overland Park, Kan., completed the UTW installation in 11 days. “The pavement – now over two years old – is holding up well and presents a very nice ride,” Coffman says.
Howard Penrod, public works director for Independence, Mo., also uses UTW in certain situations. “Concrete is effective for a long time,” he says. “We’re not reworking it every year or every other year. Based on what we’re seeing so far, we estimate the UTW should last 10 to 15 years.”
Independence also has experimented with a new method of loop placement in the UTW. “Instead of sawing them in, we laid the loops down ahead of the paving, and it worked well,” Penrod says.
Additionally, UTW provided a long-term solution for three Kansas cities when it was used at the intersection of College and Pflumm streets. Lenexa, Olathe and Overland Park meet at the intersection, which had last been repaired 10 years ago. “There was severe rutting and utility settlement around the manholes,” says Lenexa City Engineer Mike Novak.
The municipalities agreed on UTW, and the intersection was paved in September 1996. The work was completed over a weekend to avoid interfering with workday traffic flow. Now facing its fourth winter, the intersection has not required further repair. “Other than tire marks on the pavement, it looks exactly the same as the day we opened it,” Novak says. “It’s performing like a champion.”
Following the success of the joint project, Novak later used UTW at a Lenexa intersection that accommodates more than 100,000 vehicles each day. The technique has worked well in the traffic-heavy area, he says.
– Lon Hawbaker, director of streets and local roads for the American Concrete Pavement Association, Skokie, Ill.