Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/142598
Photo courtesy of Watson Asphalt Paving Company RoadScience HMA mats will cool quickly in cold or wet ambient conditions, making getting density near impossible, which can lead to raveling; but oscillation compaction can achieve density on cooled mats. Stripping is sometimes indicated by the presence of raveling, popping out of aggregate or flushed areas on the surface of the OGFC pavement, accompanied by shoving or roughness in the wheel path, they say. Techniques to evaluate stripping include coring the area, visual inspection, and measurement. "One respondent noted that his district has not experienced stripping since using crumb rubber," they say. OGFC technology continues to evolve. New research indicates heavier tack coats will suppress raveling of OGFCs, say Nam Tran, Buzz Powell, P.E., and Richard Willis, National Center for Asphalt Technology, David Timm, P.E., Auburn University, and Gregory Sholar, P.E., Florida DOT, in their 2013 TRB paper, Effectiveness of Heavier Tack Coat on Field Performance of Open-Graded Friction Course. "Compared to a conventional hot mix asphalt mixture, [an] open-graded friction course is more prone to pavement distresses such as cracking and raveling, resulting in a shorter service life," they say. "One way to potentially improve the performance of OGFC is to enhance the interface bond between the OGFC and the underlying layer by applying a heavier tack coat ... [T]he results of this study showed that the OGFC layer in Section N1 in which a heavier tack coat was applied performed better than that of Section N2 in which a conventional tack coat was used. Heavier tack coats are recommended to improve the performance of OGFC surfaces." • Horizontal "live bottom" conveyor discharges material safely even while working off-road, under high line wires, under bridges, and in tunnels. • Discharges up to 23 cubic yards of asphalt per minute. Conveyor speed is controlled from the cab. • Insulated side walls keep asphalt hot during transport and unloading. • Optional metering gate delivers low rates of asphalt or aggregate for patch work and shoulder work. Manufactured by Highway Equipment Company in Cedar Rapids, Iowa. For more information and to locate your dealer visit www.highwayequipment.com or call 800-363-1771. Text INFO to 205-289-3789 or visit www.betterroads.com/info 18 July 2013 Better Roads RoadScience_BR0713.indd 18 6/26/13 3:29 PM