Better Roads

December 2014

Better Roads Digital Magazine

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Better Roads December 2014 7 Photo courtesy of TRB SHRP2 meeting of the Midwest Pavement Preservation Partnership. Some 165 delegates from 30 states and Canada attended the three-day workshop and learned of ongoing research in preserving high-traffic volume roadways, and the reliability of existing applications in states from coast-to-coast. The defining moment of the workshop was an excur- sion to the vast MnROAD pavement test track some 40 miles northwest of Minneapolis. MnROAD is composed of a 3.5- mile mainline interstate highway (I-94) that carries 29,000 vehicles per day with 13 percent trucks; a 3.5-mile bypass interstate for live traffic diverted off the main line when it is undergoing construction and analysis; and a 2.5-mile closed- loop, low-volume roadway served by an 80,000-pound, five-axle tractor-trailer for live loadings. At MnROAD, attendees witnessed the durability of actual preservation treatments placed on the portion of the Mn- ROAD facility which carries actual interstate traffic, which had been diverted to the bypass for work on the test sections and for the visit. Minnesota DOT is one of 14 road agencies that received funding for the initial testing implementation of R26 methods. MnROAD has 50 different test sections of both rigid and flexible composition. Research is sponsored by state DOTs, the Minnesota Local Road Research Board, FWHA and private industry. MnROAD is in its second phase of research, and is developing its third phase, scheduled for 2016. "MnROAD is a long-term pavement testing facility that gives researchers a unique, real-life laboratory to study and evaluate the performance of materials used in roadway con- struction," said Jerry Geib, P.E., metro pavement and materials engineer, Minnesota DOT, at the workshop. Preservation treat- ments seen by delegates at MnROAD included flexible micro surfacing, ultra-thin bonded wearing course, thin warm mix asphalt overlays, chip seals, and the Next Generation Concrete Surface of specialized concrete pavement diamond grinding. The Partnership of MnROAD, NCAT Another highlight of the R26 workshop was the announce- ment of a new partnership between MnROAD and the National Center for Asphalt Technology (NCAT) Test Track in Auburn, Ala. Using real-world accelerated pavement preservation performance testing, this new partnership will advance preservation techniques for high-volume roadways, both asphalt- and concrete-surfaced, in both cold and warm weather climates. The new partnership will have the ability to deliver re- search products for a larger base of supportive agencies and private sector clients at lower buy-in costs. Thus the col- laboration has the potential to play a much larger role in the national effort to validate pavement performance. "Working together will help validate what's done at our facilities both north and south," says Benjamin Worel, P.E., MnROAD operations engineer. "MnROAD has built test pavements in the north and obtained results which southern states sometimes say do not pertain to them, because we're in a northern climate. The same thing goes for the northern states utilizing results from NCAT. But working together will allow more states to accept and use our combined research results and get more involved with both facilities." By contrast with MnROAD, NCAT studies asphalt pave- ments only. NCAT has 46 different test sections on its 1.7- mile oval track. Sections are sponsored on three-year cycles by state DOTs, FHWA, and private industry. Sponsors have specific research objectives for their sections, and shared ob- jectives for the whole track. The focus of research at the track has grown in conjunction with NCAT's expanding mission from just mix performance in the original 2000 research cycle, to both structural performance and pavement preser- vation in the just-ended (2012) fifth research cycle. Thus recently, pavement preservation research has been a big part of NCAT's mission. Pavement preservation research at NCAT began in the sum- mer of 2012, underwritten by seven state DOTs, and FP 2 Inc. The two current publications of the R26 project – Preservation Approaches for High-Traffic-Volume Roadways, and its companion report, Guidelines for the Preservation of High-Traffic-Volume Roadways – provide a snapshot of where high volume pavement preservation is now, and highlight a path to the future.

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