Tremendous savings can benefit local governments if they can reliably use these CIP recycling processes. "They will be able to reclaim and reuse their old asphalt pavements," Thompson says. "You can use them as a road base with a 3-inch hot mix asphalt surface, as here, or you can go through an existing thin asphaltic concrete surface and blend it with an aggregate base, and the total blend of AC surface plus agg base can be stabilized with either emulsion or foam. It's very cost-effective and allows you to maximize your in-place recycling potential. And while we're not evaluating them for our study, there are environmental problems that cold in-place recycling can solve."
Recycling very deep lift
Dunn's machines were recycling a very deep layer of existing HMA pavement, anywhere from 10 to 14 inches thick, 22 feet wide. Also, the road was being widened 3 feet on each side.
"Using a W 2000 and W 1900 we milled two inches of asphalt off the existing pavement and placed it in a widening trench that was cut with a Wirtgen W 1900 Combo cutter," says Phil Koeberlein, P.E., project manager, Cummins Engineering Corp., Springfield, IL. The widening trenches were 10 inches deep and 3 feet wide, each located 11 feet off the centerline. Then, after the millings were placed directly off the cold-mill conveyors, the existing 11-foot lane and the new 3 feet of millings were cold in-place recycled as one in two passes.
"Use of the two Wirtgen machines was fundamental to the process," Koeberlein says "Besides normal day-to-day traffic, this road leads to a local limestone quarry which handles 350 to 400 loaded trucks per day. We had to keep this road open to traffic, and needed to do one lane at a time, as quickly as possible. Having the two machines we were able to pulverize in one day and process the length of the job in one day, 10 inches deep."
The cross section of recycled material is 28 feet wide, paved 26 feet wide. The lanes are striped for 22-foot-lanes and 2 feet of paved shoulders, along with 2-foot aggregate shoulders outside the finished pavement.
Success on Hwy. 1 was assured by the recycling contractor, which orchestrated the flow of trucks, equipment and materials.
"The biggest challenge is getting the trucks lined up, with good people who know what's going on," says Tim Milhauser, senior construction manager, Soil Modification & Stabilization, Dunn Co. "Compaction is key to the success of a full-depth project like this, and everyone must be in synch."