Better Roads

October 2013

Better Roads Digital Magazine

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asphalt pavement (LLAP), also known as Perpetual Pavements. Building on the success of a project on the truck-heavy 710 Freeway in Los Angeles County, Caltrans designated the two stretches of I-5 for the design strategy and later put out a long-life asphalt pavement project on Interstate 80 between Sacramento and the San Francisco Bay Area. Other potential candidate projects are in the planning stages. "The Department is excited about the progress being made in the long-life pavement arena," says Peter Vacura, chief of asphalt pavement for Caltrans. "With the development of the mechanistic-empirical design methodology, we can design and construct 40-plus year-life pavement with greater reliability, lower cost and less long-term maintenance." The Asphalt Pavement Alliance (APA) defines long-life asphalt pavement as "an asphalt pavement designed and built to last longer than 50 years without requiring major structural rehabilitation or reconstruction and needing only periodic surface renewal in response to distresses confined to the top of the pavement." Long-life asphalt pavements offer several advantages over conventional pavements, including lower life-cycle cost, lower user-delay costs, reduced environmental impact and greater worker safety. The roots of the LLAP movement in California can be traced back to a presentation in 1995 by Caltrans materials engineer Bill Farnbach, who announced the department was looking closely at longer-life pavement strategies. Next, a location to try out the strategy was identified: the Long Beach Freeway, or I-710, where tens of thousands of cars and trucks jockey for position near the massive Port of Los Angeles-Long Beach complex. It was one of the toughest tests imaginable. The dual port together handles more than 40 percent of the nation's Asian imports and ranks as the sixth busiest container port in the world. Caltrans estimates the adjacent freeway carries in the neighborhood of 150,000 vehicles a day near Pacific Coast Highway, of which about 16 percent are big rigs heading to and from the port facilities. The I-710 Freeway Rehabilitation, as it became known, began in 2001 and represented a number of "firsts" for the 117-year-old department – the first LLAP project in California, as well as the first use of 55-hour weekend closures to minimize inconvenience to commuters due to construction activity. In addition, as reported in the 2005 issue of California Asphalt magazine, the project was the first time the department used analytically based (mechanistic-empirical) pavement PMA was used in the top 3 inches of this project, and AR-8000 was used in the other layers, including the 3-inch-thick, "rich bottom" layer. The variability in structural pavement thickness is concentrated in the varying thickness of the middle layer(s). design for both the replacement and overlay pavement structures. As part of the design methodology, the Strategic Highway Research Program (SHRP) developed shear and fatigue tests for use in the evaluation of the hot-mix asphalt (HMA). Moreover, the special provisions in the contract required the contractor supply the results of shear and fatigue tests for the mixes proposed for use. The requirement was to ensure the mixes actually used exhibited equal or better characteristics than those of the mixes used to design the pavement sections. Also, the compaction requirements for the HMA layers were more stringent than those regularly used by Caltrans. Chris Gerber, vice president of the infrastructure division for Twining, has vivid memories of the high-profile I-710 project once construction got underway. "One weekend, there were 26,000 tons of HMA produced from two separate HMA plants," Gerber recalls. Twining performed material testing on the project and managed the Better Roads October 2013 19 HighwayContractor_BR1013.indd 19 9/30/13 2:08 PM

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