Palmer Paving Corp., which was founded in 1955 by Charles M. Callahan Jr., milled and paved 96 lane miles of I-90, the Massachusetts Turnpike, just west of Springfield, MA, and the technology solution employed to deliver the job paid off.
The paving contractor executed a 2-inch-deep cold milling of the existing asphalt surface, then followed with a "shim" or leveling course prior to placement of a 2-inch surface wearing course overlay.
"The existing asphalt was cracked and broken. Normal wear and tear had taken its toll. The pavement was not oxidized or raveling, but was delaminating with quite a few cracks. It was due for replacement," says Rob Mucha, project supervisor, Palmer Paving Corp., Palmer, MA. "We paved a total of 24 miles, two lanes each way, plus the breakdown [shoulder] lane."
The project was enhanced by the use of oscillation compaction via a new HD+120 VO roller, which boosted the speed of placement, and two HD 110 VHV high-frequency rollers, all from Hamm Compaction Division of Wirtgen America Inc.
A 10-foot Vision 5203-2 wheeled paver from Vögele America Inc. was used to place hot mix asphalt. They're among three Hamm rollers and two Vision pavers - the other being an 8-foot 5100-2 tracked paver - used by Palmer in 2009.
Removal of existing pavement
To remove the old asphalt to a depth of 2 inches, Palmer used two W 2000 cold mills from Wirtgen America Inc., one with a standard 6-foot 6-inch drum, and the other with a 7-foot 3-inch offset drum.
State specs recommended that the milled surface be overlaid within seven days. "They do not want the milled surface to become raveled, in case the 2 inches removal did not get down to good, solid material." Mucha says. "We hold to that standard for our own purposes, because raveling will open up a can of worms."
Standard bit spacing was used. "Micro-milling has been done in this state to correct an error in paving," Mucha says. "But micro-milling as a standard practice we have not yet seen in Massachusetts.
"The offset drum is useful for city work, giving us the ability to offset away from the curb," Mucha says. "When running it down the curb in the city, we are kept away from the trees, fire hydrants and street signs. It pushes the machine farther into the roadway. In the city we will get trees right on the belt, and the operator can wind up in the branches. It also can mean one less pass for a machine just to catch two or three feet. That means a lot in time."
Placement of asphalt lifts
On the MassTurnpike, following milling, a 14,000-ton shim course was placed 3/4-inches above the substrate and compacted to about 1/2 inches in depth.
"The shim course is placed to take out any irregularities or ‘scabbing' between layers that may result from the milling," Mucha says. "It results in a smoother surface on which to place the top course. The shim mix is a denser mix than the surface course. Because we only place it 3/4-inches thick, we don't use larger aggregate." Top-size aggregate in this leveling course was 3/8-inch NMAS. A compaction factor was not required for this thin lifoot
The paver used on the I-90 project was rubber-tired Vision 5203-2, but Palmer also owns a tracked Vision paver.
"When you need to move a paver during or at the end of a day a sizeable distance down the road, or park it or move it off the road, you don't want to be running tracked pavers any farther than you have to," Mucha says. "You want to get down the road as quick as you can, and get off the road as well. A rubber-tired paver in that respect will work a little better than the tracked."
Palmer's Vision 5203-2 has a Carlson screed and built-in Niveltronic high-performance leveling system with averaging skis from Vögele AG.
"We are working for a smoothness bonus," Mucha says. Ride quality was the only mix property with a bonus clause; and preliminary data indicates nearly the full potential of 110% of pay was achieved on this project.