Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/85926
Asphalt Recycling Section by Daniel Brown, Contributing Editor Cold in L.A. C CIR plus microsurfacing get the job done old-in-place recycling (CIR) followed by micro- surfacing was not only a cost-effective treatment for Los Angeles County when it encountered un- stable pavement conditions in one of its roads, but CIR was the perfect green solution. At issue is Upper Big Tujunga Road, a 9.5-mile, two- lane mountain road in a remote location in the Angeles National Forest. The CIR treatment, going 3 inches deep, followed by microsurfacing, cost the county approxi- mately $750,000. The LA County Department of Public Works encoun- tered problems with the road when it applied a chip seal in October 2010. The U.S. Forest Service required that the preservation work be done late in the year. "With cooler weather, it was not an optimal time to apply the cationic high-fl oat emulsion with 5/16-inch chips," says Imelda Diaz, Civil Engineer with the County. Upon ini- tial placement of the chip seal, some of the chips rav- eled off, so the County raised the amount of emulsion, applying up to double the amount specifi ed at fi rst. That seemed to have solved the problem. Then in April 2011, the Los Angeles area encountered a period of hot weather. "The pavement started moving; it became soft and gummy," says Diaz. "The emulsion in the chip seal may not have fully reacted when it was fi rst placed in the cooler months of October and November, and remained dormant through the winter. Then in April when we got that hot spell, the heat seemed to have ac- tivated the emulsion in the chip seal. So essentially it was like rock fl oating in the emulsion." Now the road was unsafe, especially for motorcycles. So the County closed Upper Big Tujunga Road for a time, and sought answers from contractors and suppliers in the 28 July 2012 Better Roads area. It turned out that Pavement Recycling Systems (PRS) was doing some cold-in-place recycling work on the nearby Angeles Forest Highway. "That got us thinking, 'What if we used cold-in- place recycling to fi x this problem on Upper Big T?'" recalls Diaz. "We wouldn't have to haul in new materi- als, and if we could recycle what is there, that's more viable than trying to remove everything and replace it with hot mix. Because most CIR treatments require a wearing surface, microsurfacing seemed like the best alternative." "So essentially it was like rock floating in the emulsion" - Imelda Diaz, LA County DPW So the county consulted with Pavement Recycling Systems and with Doug Ford, President of Pavement Coatings (PCC), a Jurupa Valley, Calif., company that per- forms microsurfacing. The CIR work was then performed by PRS and the mi- crosurfacing was per- formed by PCC as sub- contractors to Torres Construction. Only about half of Upper Big Tujunga required CIR work – 9 lane miles to be exact. The CIR was only needed on the half with ex- cess asphalt on the road. "The high asphalt content on the road was initially a danger, and then it became an asset," said Doug Ford. "With the cold-in-place recycling we ran 1.6 percent emulsion, but without that additional asphalt we would have run 2.5 percent or more of emulsion." The CIR Train "Leading off the CIR train was a Caterpillar PR 1000 mill- ing machine, working 3 inches deep and 12.5 feet wide. The mill conveyed the material back to a recycler, which has screens and a crusher to reduce all recycled asphalt to 1-inch-minus," says Chris Rogers, Superintendent for Pavement Recycling Systems. "When the material has