Slurry Pavers grading the 12-in. FDR layer using a GPS-controlled grader.
Just south of Staunton, Va., in Augusta County, a unique in-place pavement recycling project is currently progressing under the supervision of the Virginia Department of Transportation (VDOT), Staunton District.
VDOT and its contractor, Lanford Brothers Inc., of Roanoke, began the project in late March. Its purpose is to rehabilitate and repave a section of southbound Interstate 81 between exits 217, Mint Spring, and 213, Greenville in Augusta County. The contract is valued at $7.6 million.
According to a VDOT press release, “This is one of many sections of I-81 where the entire structure of the pavement, extending two feet below the surface, has deteriorated from more than 40 years of high traffic volume, and its accompanying heavy vehicle loads have cause the roadway’s wet foundation to rapidly deteriorate.”
The press release noted that VDOT planned to employ a specific combination of reconstruction processes that had the potential to change the way the aging road system was rehabilitated. Three specialized processes were planned to recycle the existing pavement materials at the site and reuse them.
“This will be the first time all three processes will be used together on a single pavement reconstruction project in the United States and implements research by the Virginia Center for Transportation Innovation and Research, VDOT’s research division,” the release continued.
The contract was awarded on Dec. 10, 2010, and a completion date is set for November 2011. The road area includes 3.6 southbound miles from mile marker 217.6 to mile marker 214. The full project includes pavement rehabilitation, guardrail, underdrains and rumble strips.
“Recycling the existing road material not only eliminates the need for numerous truck trips to haul stone and paving materials to and from the site, but also allows the causes of the deterioration to be addressed rather than just the symptoms,” a VDOT spokesperson said. “In-place pavement recycling is much more cost effective and should greatly increase the pavement service life. The process is more environmentally friendly in that fewer loads of material will be trucked to and from the site and less new material will be required thereby reducing the greenhouse gas emissions. The process has quicker completion times, which reduces the traveling public disruptions.”
For the project, the following work was done. On the right lane, the top 10 in. (25 cm) were milled, hauled to an on-site recycling plant, processed (on-site) and repaved using traditional paving equipment. The next 12 in. (30 cm) were recycled in place while the milled material was being processed. This allowed for the pavement to be strengthened to a depth of approximately 22 in. (55 cm). The left lane, which had less deterioration, was recycled in-place to a depth of 5 in. (12.7 cm).
The milled material from the right lane was processed using a cold central-plant recycling technique. The top 10 in. (25 cm) of existing road material was milled and transported to a mobile recycling plant where it was mixed into a foam stabilized base course. The 12-in. aggregate layer below was stabilized in place using a full-depth reclamation process that strengthened the pavement substructure by adding a stabilizing agent. This layer was then re-compacted to support the foamed asphalt from the mobile plant, which was delivered in dump trucks and repaved using traditional paving equipment. The right lane also received 4 in. (10 cm) of intermediate hot-mix asphalt, and will receive an additional 2-in (5 cm) SMA overlay as the final riding surface.
In the left lane, a cold in-place recycling method was employed. In this process a Wirtgen CR 3800 12-and-a-half ft. (3.8 m) machine was used. This machine mills the pavement 5 in. deep, foam stabilizes the milled material and places it through and attached paving screed in one operation. The left lane was overlayed with a 2-in. intermediate hot-mix asphalt course and will receive an additional 2 in. SMA overlay as the final riding surface.
According to Al Soltis, vice president and division manager of the roadway division of Lanford Brothers, time created a challenge with the project.
“We had a five-day window in which we were allowed to close down the roadway,” he noted. “We had to always pick our days when the temperatures would allow us to work and the chance of rain was low enough for us to take a chance of doing it. If you’re opening up a section of the interstate 22-inches deep and you have a significant downpour, it would take a long time to dry out, and there were very significant penalties if we did not open on time.
“We were allowed to close the road for different closure periods. We were allowed to close the road down at 9:00 Friday, and it had to be opened back up by 7 a.m. the following Thursday. Thursdays and Fridays were the heaviest traffic times in this area, so we had to always make sure that we could get our work done in time so that we could be open during those peak times.”
Throughout the job, cooperation has been a key element.
“I would say that one of the major reasons I would give for our success so far is that this was a partnering project where we came together as a group,” Soltis said. “Once the project was awarded, we spent time identifying what all the problems were. It helped for the highway department and all of us in the contracting group to understand the interactions between the different types of equipment that we had and what kind of space requirements would be needed. We just had a very, very good understanding of who was going to do what, and we stayed out of each other’s way to do it. When each team member came on the job, they had the opportunity to do their job to the best of their ability, and we knew how we could help one another to succeed. I give a large degree of credit to the partnering process. We had a good group, and the good Lord has shined very well on us so far.”
Soltis noted that three values were set for the project: safety, quality and value.
In the right lane, 10 in. (24 cm) of existing pavement was milled 14 ft. (4.2 m) wide to the required cross slope. Lanford Brothers Co. utilized two milling machines, a Wirtgen W210 and a Wirtgen W2100, both utilizing slope control.
For the 12-in. stabilization after milling, Slurry Pavers utilized a WR2400 recycler, two cement trucks, a water truck, a 15-ton (13.6-t) pad foot roller, and a Cat grader with GPS controls.
The 6-in. (15 cm) recycled foamed asphalt base was mixed by Lanford Brothers utilizing a Wirtgen KMA 220 mobile recycling plant. It was placed by B & S Contracting utilizing standard paving equipment.
The 4 in. intermediate asphalt mix was placed in two lifts, produced and placed by B &S Contracting Inc. Staunton, Va., utilizing standard paving equipment.
In the left lane, 2 in. of milling of existing pavement was done 12 ft., 6 in. wide by Lanford Brothers.
The cold in place recycling at a 5-in. depth was done by Reclamation Inc. utilizing a Wirtgen CR 3800 recycling, two Hamm HD 120 rollers, and one Hamm GRW 280 rubber tire roller, a cement truck, and two asphalt tankers.
A 2-in. intermediate asphalt mix was produced and placed by B&S Contracting.
Miscellaneous work included under drains by Curtis Contracting, line stripping and traffic control devices by Sandra’s Marking Company, and guard rail by Landford Brothers Co. CEG