Installing ultra-thin whitetopping is similar to placing new pavement. The concrete bonds to the asphalt, which — when combined with short joint spacing — reduces stress and in turn makes it possible for the pavement to bear heavier loads than new asphalt placed on new subbase.
Credit: Photo: Village of Lombard
To prevent cracking, Schwab says it's important to use short joints and begin sawing as soon as possible using lightweight, early-entry saws for both transverse and longitudinal joints. A National Cooperative Highway Research Program 2004 review recommends that joint spacing be 12 to 18 times the thickness of the concrete panels.
The new pavement was placed in 4-foot square panels with polypropylene fibers added to the mixture at a rate of 5 pounds of fiber per cubic yard of concrete. “The fibers add sufficient strength to support the high traffic counts,” Schwab says. According to ACPA's Illinois chapter the fiber makes resurfaced pavement about 20% stronger than new concrete.
Many businesses in the industrial park operate two shifts, six days a week. To avoid disrupting traffic, engineers decided to place the pavement one lane at a time so crews could get in and out of the jobsite. After 3 to 5 days of curing, ready-mix trucks drove on the new slab to deliver concrete for the other lane.
Crews worked 8 to 12 hours a day from late July 2010 through November. Landscaping will be completed this spring.
The public works department used Twitter, e-mail notifications, and newsletters to keep residents and business owners updated on the progress of the project.
— Fielding is a former editor of PUBLIC WORKS.WEB EXTRA
To watch a video of the ultra-thin whitetopping process, click here.