Asphalt Recycling Section
S.H. 7 is the main access road to the famous Carlsbad Caverns National Park. Although it is a New Mexico state highway, the road’s location in a national park meant that the job fell under the jurisdiction of the Federal Highway Administration. FHWA’s engineer for the project was Eric Zeller, P.E., project engineer for the Central Federal Lands Highway Division.
Field work began when McDade sampled the S.H. 7 roadway for mix design purposes. By using a Wirtgen WR-2400 recycler to reclaim to a depth of 8 inches, the mix consisted of 50-percent asphalt and 50-percent caliche base. Mix design testing was done by Maghsoud Tahmoressi of PaveTex Engineering and Testing in Dripping Springs, Texas.
Mix design testing showed the optimum emulsion content for the roadway was 3-percent. Constructors Inc., the subcontractor for the FDR and overlay, incorporated PASS-R, a patented engineered emulsion developed by Western Emulsions Inc. (WEI) and supplied by their Roswell, N.M. facility. The on-site representative for WEI was Larry Parker, regional marketing manager for the New Mexico region.
The prime contractor for the job was Briston Construction LLC, from Tempe, Ariz. Briston’s superintendent was Jard Plocher and the project manager for Constructors Inc. was Cory Burnett.v
Budget Stretching in Ingham County
Even though the hot-in-place recycling (HIR) process plus an ultra-thin overlay cost about the same as a mill-and-fill, William Conklin says the HIR process gave the Ingham County (Michigan) Road Commission a better product in the end.
Briefly, the HIR process heats the pavement surface and rejuvenates it in-place.
“We decided that the hot-in-place recycling was the best fit for our situation and generally we have been pleased with the results,” says Conklin, managing director for the commission. “We saved the cost of milling and removal of the asphalt, and the HIR doesn’t leave a milled surface underneath the overlay. If we had only milled off the top 1 inch and overlaid that, we would have been leaving an old, brittle and cracked pavement underneath. This allowed us to restore some of the substrate properties and not worry about reflective cracking in the overlay.”
For Ingham County, the total cost of HIR plus a liquid rejuvenator was $3.34 per square yard. The unit cost of the ultra-thin overlay was $85 per ton, applied at 110 pounds per square yard or about 1-inch thick. So, the overlay cost $4.68 per square yard. That adds up to $8.02 per square yard for the HIR plus overlay.
“The cost of a conventional 2-inch milling and 2-inch paving would have been about the same cost – at $8.05 per square yard – assuming conventional asphalt costs $55 per ton and milling runs $2 per square yard,” says Conklin.
Last year, the commission turned to Gallagher Asphalt Corp., Thornton, Ill., to perform the HIR process on 7.2 miles of residential streets in Meridian Township. Most of the streets were 20 or more years old, and Conklin says their distress level really exceeded that for which Gallagher normally recommends HIR.
“By all rights some of these streets should have been milled out completely and replaced,” says Conklin. “But to stretch our budget, we decided to do the HIR process. The fact that 1.5 inches of it was recycled and closed up helped the reflective cracking from coming up through the overlay.”
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