Dig it up. Beat it up. Cover it up.

It sounds like a bad plot from a TV cop show. But it's actually an innovative pavement rehabilitation option. Ultra-thin whitetopping (UTW) is a cost-effective, long-lasting solution for revitalizing pavement. It's a proven process that works.

Whitetopping itself is not a new technology. Working well for intersections that have become deeply rutted from heavy traffic and heavy load carriers, whitetopping provides a solid fix that stands up well to both traffic and weather. Typically, the decision of whether to rehabilitate deteriorating asphalt with more asphalt or with whitetopping is made based on a comparison of initial outlay and life cycle cost. Standard whitetopping, which generally uses a six-inch layer of concrete, often is ruled out because of initial costs as well as setting time. Ultra -thin whitetopping uses new technology to cut costs, reduce setting time, and extend life cycle without jeopardizing durability.

How it Works

The asphalt surface is prepared in the same manner as if standard whitetopping were going to be applied. The road is milled, and approximately ¼ inch of the asphalt is removed to create a bondable surface for the concrete. That's the ideal. However, on roads that are particularly worn, there may be spots where there is only a gravel base remaining. Whitetopping can still be an option in such cases. The key to UTW is short joint spacing and a concrete thickness that does not exceed four inches. Short spacing combined with compact slabs aids in the distribution of stresses and minimizes joint movement and cracking. Joint sealing is not usually necessary. UTW is a very popular paving option in the southern states. However, many test projects, prove that UTW can withstand winter weather conditions as well. UTW is a good solution for parking lots as well as road work, and can be expected to last up to 15 years. But the real proof comes when you take the process to your local roads.

Start With a Challenging Project

Dennis Doan, a member of the Michigan Concrete Association and President of Ann Arbor Concrete/Doan Construction, responded last fall to an ad for bids placed by the Washtenaw County Road Commission.

The ad read: Ultra-Thin Concrete Overlay Construction on the eastbound approach of Pleasant Lake Road at the intersection with Ann Arbor Saline road. Work includes cold milling the existing bituminous surface, placing , finishing , sawing and cleaning concrete. Doan was familiar with the Ultra-thin Whitetopping process. He was also very familiar with the intersection.

The left turn lane on Pleasant Lake Road as it approaches Ann Arbor-Saline Road was extremely rutted. The heavy truck traffic accessing a local sand and gravel operation was keeping this intersection in a state of extreme disrepair. The asphalt in the turn lane had been replaced a number of times over the years, and as recently as July of 1997, but the traffic ruts kept returning. The county had concluded that the only reasonable long term fix would be a concrete overlay.

The lane to receive the UTW was 267 feet long and 13.5 feet wide. The bid specification called for the milling of four inches of asphalt and the replacement of a four-inch concrete overlay that would reach a compressive strength of 2,850 psi at 24 hours and 3500 psi at 72 hours.

Throw a Football Into the Mix

Doan received notice on September 19, 1997, that he had submitted the winning bid. "What made this job interesting," said Doan, "was that it had to be completed over a weekend when the University of Michigan was having a home game. Not only would there be increased traffic, but we all wanted to finish in time to see the game." The milling took place on Friday, October 10, and the concrete was placed on Saturday, October 11. The intersection was open to traffic on Monday, October 13, with a compressive strength exceeding 6,000 psi.

Everybody Wins

Washtenaw County Engineer, Steve Puuri, couldn't be more pleased with the results. "This intersection is probably the best test site for UTW in the County. We had totally re-done this stretch of road with base material, drainage, curbing - just nine months before, and we already had 5-inch ruts due to the heavy loads braking and turning. Given the funds available, the history of the road, and the fact that it was a real fast-track job, UTW was a logical choice. It'll be interesting to see how it holds up after the first full season. But initial indications are very positive."

The Washtenaw County project has only been finished a few months, but Doan is confident that the process was the right one for the job. "UTW is proving over and over to be stronger and longer-lasting than asphalt requiring little or no annual maintenance while providing an overall better surface. "Yet it's faster and less expensive than standard whitetopping," explained Doan.

"I really don't have a hard time recommending it to my customers for a variety of needs. It's an easy sell."