Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/440996
RoadScience 8 December 2014 Better Roads There, the life-extending benefits of pavement preservation are being defined for an array of flexible pavement preserva- tion treatments, and treatment combinations. Because NCAT's mission focuses on asphalt pavements only, the new partnership will permit testing of PCC pave- ments and the inclusion of PCC results in comprehensive research products, which is not possible when NCAT works on its own. "Our focus at the National Center for Asphalt Technology is flexible pavements," said Dr. Buzz Powell, P.E., assistant director, NCAT Test Track, Auburn, Alabama. "The partnership with MnROAD can provide us the two things that we don't have at NCAT, the two Cs of climate and concrete. In the Deep South we have a very limited climate for testing pave- ment performance, and as Ben says, our clients are primarily in the southern half of the United States, and we don't have any concrete test sections. A partnership with MnROAD lets us leverage their cold weather conditions and concrete pave- ments that constitute a big part of the preservation picture." High-volume preservation Conventionally, chip seals and other surface treatments have not been associated with high-volume arterial, collector or interstate-type pavements. Instead, with regional excep- tions, the preferred application is an asphalt overlay, follow- ing years of minimal care, typically, pothole patching and occasional crack sealing. But a variety of surface treatments for high-volume roads exists, and experts say they have the potential to prolong pavement serviceability at minimal cost. Historically, agency managers felt that the high-type asphalt and concrete pavements always needed an additional section of asphalt placed on them, and that chip seals, slurry seals and other preservation treatments would not stand up to the traffic and loadings of those high-level pavements. But the original SHRP [Strategic Highway Research Program, 1988-1993] clearly demonstrated that preservation treat- ments were fully viable for any volume of road. There are the right techniques to use, experts note; for example, the chip seal must be properly designed, with good embedment and traffic speed held down. But on the Tacoma Narrows Bridge, with about 178,000 ADT [average daily traffic], Washington State DOT has been putting chip seals on the deck for years. The owner doesn't want to add a lot of extra weight, but needs to keep friction up. Caltrans has used surface treatments on the main line pavements on I-5 and I-80, and the treatment has held up to the traffic. Such surface treatments can "afford" to have a higher quality aggregate in them, because other costs are lower. As a result, their durability can be much better. The surfacings are not expected to carry the load or provide structural value, but to ward off the effects of aging and oxidation that the environment provides. If preservation treatments are placed correctly, they will serve the pavement and traveling commu- nity in a very positive fashion, experts say. Still, preservation of high traffic pavements is not as wide- spread as for local roads, said Jim Moulthrop, P.E., execu- tive director of FP 2 Inc., at the Minnesota conference. "The practice of pavement preservation on high-traffic volume roadways is not as common as on lower-traffic volume road- ways," Moulthrop said, adding the specific treatments used on low volume roads may not be as effective on high volume pavements. "The benefits of high volume roadway pavement pres- New partnership announced in September R26 workshop will see collaboration for high-volume roadway pavement preservation research between warm-weather, all-asphalt NCAT Test Track (left) and cold-weather, asphalt and concrete MnROAD test facility (right).