Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/85926
Asphalt Recycling Section ing. The rural asphalt roadway had served for 25 to 30 years with only chip seals and some patching to main- tain it. To rehabilitate Highway 141 last summer, the Colorado Mountain S Rocky HOT tate Highway 141 south of Grand Junction, Colo., was in pretty rough shape. Sections had rutted, and there was both fatigue cracking and alligator crack- Department of Transportation (CDOT) elected to use hot-in-place recycling on the top 2 inches followed by a 2-inch hot-mix asphalt overlay. By heating, remixing and repaving the top 2 inches of the existing roadway, CDOT fi gures it saved 38 percent – compared to cold milling the top 2 inches and replacing it with a new asphalt overlay. "At the time we were looking at paying $600 to $700 per ton of PG 64-22 liquid asphalt cement," says Devin Ray, CDOT project engineer. "That put our cost for new hot mix at $60 per ton. So it cost us $11.65 per square yard for the 2 inches of asphalt overlay. By comparison, the hot-in-place recycling – including the virgin mix that we added – cost $7.27 per square yard. So that's a 38-percent savings right there. And we got a rehabilitated road that is structurally comparable to all-new asphalt." Lee Smith, president of the hot-in-place recycling (HIR) subcontractor Paveover, Albuquerque, N.M., says Highway 141 recycled well. "You've got to use the right process on the right road at the right time," he says. "This is a case where they did that. Even if the cost of the hot recycling was the same as cold milling with an 30 July 2012 Better Roads by Daniel Brown, Contributing Editor For Colorado's State Highway 141, CDOT goes with HIR overlay, the hot-in-place recycling is a good thing to do. It saves substantial amounts of new aggregates and virgin asphalt." The general contractor was Mays Construction Specialties in joint venture with United Companies of Mesa County, Colo. CDOT's Ray says he likes the in-place heating and remixing process. "I think you can do a lot with your smoothness too, because the recycling train allows you to add virgin mix to smooth out ruts or replace the asphalt in low areas," says Ray. In fact, Ray says the smoothness and overall quality of the new roadway won an award from the Colorado Asphalt Paving Association – Best Overall Quality for Rural Resurfacing. Multi-Machine Train The total project consisted of 22 lane miles of two-lane roadway. Paveover performed its HIR on 168,246 square yards of pavement. The fi rst two machines in the HIR train are preheaters. Sometimes only one is needed, but on Highway 141, Paveover used two. Both machines ap- ply intense heat using banks of propane-fueled infrared heaters, says Mike Smith, Paveover project administrator. The next machine, called the A unit, is a heating-and- milling machine that mills the pavement to a depth of 1 inch and places it into a windrow. "The next thing that happens is that the second heating-and-milling unit shows up and that's what we call the B unit," says Mike Smith. "The B unit has a windrow pickup machine that