Pavement Recycling Inc. of Rochester, Mich., uses three processes to reclaim county road bases in-place. All methods feature pulverization of old asphalt using two reclaimer-stabilizers. With one method, emulsion is added to rejuvenate and stabilize the base; another method uses liquid asphalt cement and a third adds calcium chloride solution.
In Saginaw County, Mich., officials figure it costs $78,839 per mile to rebuild two-lane roads with emulsion for the base, including 3 1¦2 in. of hot-mix overlay. The liquid asphalt method runs $92,385 per mile with the same overlay, says Jim Lehman, Saginaw County highway engineer. By contrast, he pegs complete remove-and-replace costs at $350,000 to $500,000 per mile, depending on drainage and grading requirements.
Lehman is enthusiastic about in-place reclamation. "I wouldn't do these roads any other way," he says. "Reclaiming lets us generate a better road system because we can do more with the money we have. If we had to excavate and rebuild them all, it would take a lot longer to put our roads in shape."
Because reclaiming offers a low-cost alternative, the county is able to reserve complete reconstructions for worst-case roads. And in some cases, Lehman says the county contracts for milling and hauling reclaimed asphalt pavement (RAP) to nearby locations for use in base construction.
For those jobs, the county figures RAP costs a minimum of $9 per ton for hauling to a second location. That $9 holds whether the county buys the RAP from a contractor or mills the material from one project, then hauls it to a second location nearby. In Saginaw County, $9 per ton is not especially low-virgin aggregate costs $8.40 per ton. "We can get limestone off the docks, and it's almost cheaper for us than to use millings," explains Lehman.
Pavement Recycling Inc. uses its two CMI reclaimers, an RS-500 and a new RS-650, for all three of Saginaw County's reconstruction methods. In August the company reclaimed a 2 1¦2-mile project along Frost Road in the county, and a CMI representative visited the job to see the contractor's new reclaimer in action.
"Production with the 650 runs up to 30% more than with the RS-500," says Gary Van Hevel, vice president of Pavement Recycling. "Between the two machines we ground up two miles of two-lane on Sharon Road between 7 a.m. and 2 p.m." In average-to-difficult conditions, Van Hevel figures the 650 can grind 6,000 sq yd per 10-hour day, moving at about 15 fpm. At one project in Huron County, the reclaimer churned along at 40 fpm, cutting asphalt 7 in. deep.
Because Michigan's county roads have been built and resurfaced to such variable depths, Van Hevel appreciates the ability of his company's reclaimers to cut at different depths on each side. "We had one road with 2 in. of asphalt on one side and 8 in. in the middle," he says. "That road was crowned like a turtle's back. The ability to cut different depths on each side allowed us to crush just the asphalt and good base material without going excessively deep on the side that was 2 in. thick."
Aged asphalt pavements can run deep in Saginaw County, and thicknesses vary. On Frost Road, the 650 worked at about 15 fpm, cutting 9 in. deep on one side and 10 in. on the other. As the two machines moved along, the 650 slowly gained ground on the 500 cutting at the same depth.
"I like it a lot," said 650 operator Chris Chapman. "It cuts this tough asphalt pretty good. It maneuvers really well, and you can crab-steer while the cutter is running. That makes it easier to get over to the next cut in parking lot work."
At Frost Road, the contractor used three passes with the 8-ft-wide reclaimers to handle the 22-ft road. The project consisted of 31,734 sq yd of reclamation.
Like Chapman, 500 operator Ed St. John praises his reclaimer. "It's a nice machine," he says, noting that the machine handily cuts 7 to 10 in. deep at 10-12 fpm. When visited, the two machines were grinding material to 1 1¦2 in. minus.
Following pulverization, the base is compacted and shaped. Next in the process comes stabilization with a P&H multiple rotary mixer. The four-drum machine is not made anymore, but Pavement Recycling typically uses one such model to incorporate liquid asphalt at 1 3¦4 gal per sq yd, to a 6 in. depth, says Van Hevel. That is about 2.25% AC by weight of reclaimed material.
For the emulsion process, initial pulverization is followed by grading, compaction and the addition of 3 in. of aggregate. Fitted with an additive package, the reclaimer next applies emulsified asphalt or other additives at specified rates, and stabilizes the base. Saginaw County puts the cost of virgin aggregate at $16,700 per mile, so the total cost for the emulsion method runs somewhat higher than base stabilization with liquid AC.
After the stabilizer material is added and mixed, "we grade, compact and call Saginaw Asphalt," says Van Hevel, referring to a local paving contractor.
The reclaimers "do a good job," said Jerry Turner, chief inspector for Saginaw County, while observing the two machines work Frost Road. "We're satisfied with their work."