The innovative construction methods the Virginia Department of Transportation (VDOT) is using to rebuild part of Interstate 81 in Augusta County will reduce construction time by two-thirds, save VDOT millions of dollars and recycle existing road material back into the new pavement.
VDOT’s research facility, the Virginia Center for Transportation Innovation and Research (VCTIR) in Charlottesville, has studied a number of pavement rehabilitation techniques and has recommended widespread use of innovative recycling processes throughout the commonwealth.
“VDOT will employ a specific combination of reconstruction methods that has the potential to revolutionize how we rehabilitate our aging roads,” said Dr. Brian Diefenderfer, a VCTIR pavement researcher. “We are using three specialized processes to recycle existing pavement materials at the site and reuse them as we rebuild the pavement. This is the first time the three recycling methods will be used together on a single pavement reconstruction project in the United States.”
The project will rehabilitate a 3.7-mile section of southbound I-81 between exits 217 and 213 just south of Staunton. It is one of many segments of I-81 where the entire structure of the pavement, up to about two feet below the surface, has deteriorated from more than 40 years of high traffic volumes and their accompanying heavy loads.
The construction work on this “in-place pavement recycling project” is expected to take two months to complete; the entire project will take eight months and cost $7.64 million. Traditional construction methods for this project could taken up to two years and cost more than five times the contracted amount. VDOT would have had to widen the southbound lanes, including the bridges, to allow two-lane traffic during the reconstruction. The savings derive primarily from the reduction in time and reuse of materials already in place within the pavement.
On this stretch of I-81, the right lane must be restored from the asphalt driving surface down through its foundation (a combination of compacted aggregate and subgrade soil). Since most heavy traffic loads use the right lane, it has more underlying damage than the left lane.
“Unless the foundation under the right lane is rebuilt, simply repaving the surface is only a temporary fix,” Diefenderfer said.
The project will strengthen and re-compact the 12-inch underlying foundation in the right lane using “full-depth reclamation.” VCTIR worked with VDOT to conduct three recent pilot projects employing this process. An upcoming VCTIR study documents the results and “lessons learned” from these pilots and recommends using full-depth reclamation on other pavement rehabilitation projects where major structural problems exist.
The asphalt layer under the driving surface will be restored using “cold central-plant recycling.” In this technique, stockpiled milled asphalt from the road is processed in an on-site mobile plant for reuse under a new hot-mix asphalt overlay.
Because the damage to the left lane is less severe, it only requires treatment to the surface and underlying asphalt layers. “Cold in-place recycling” uses a machine to pulverize the asphalt layer on the road, then strengthen and re-compact this reconstituted material on top of the foundation before a new asphalt overlay is put down.
Savings on the I-81 in-place paving recycling project go beyond time, money and materials. It will save fuel because it reduces the need to transport as much new and old materials. It will increase safety for both drivers and road workers on the project, because it will cut back on work-zone congestion. This section of rebuilt pavement also will be stronger from bottom to top, extending its service life and reducing the need for such complex maintenance for many years.