Better Roads

October 2013

Better Roads Digital Magazine

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RoadScience Photo courtesy of Transtec Group including the redesign of the drum end ring configuration for (MTV), which keeps hot mix hot while fighting mix segbetter match-cutting and increased tool life, the impact angle regation and keeps the paver moving forward without the of all of the tools on the drum was adjusted to optimize the roughness-inducing jolt of truck against paver. This also means life of the consumable bit. saying goodbye to wheel locks, which bind the front of the The "lacing" pattern was adjusted to provide a better texpaver to the rear wheels of the dump truck. ture on the milled surface, as well as a more balanced impact The Asphalt Institute recommends operating the paver speed and feed gates to keep the augers turning 85 percent when the cutting tools strike the surface. of the time, keeping forward motion at least 75 percent of The variety of grade and slope controls available to opthe time and maintaining feed augers with proper head and erators of cold mills is wide, but they all assist operators in uniform flow of material to the screed. achieving smooth, predictable cuts. Once the paver is in motion, it should stay in motion. Then, "Every job is different, and the operator today has the opautomatic screed and grade controls using averaging skis will portunity to select the type of grade control system he wants attain exceptional smoothness to use," Wiley says. "It could in the final pavement, so long be a laser system, running as compaction is executed coroff stringline, GPS, dualrectly. grade, grade-and-slope, averLate last season, a pair of aging, averaging with three high-performance pavers were sensor heads or seven sensor attaining astonishingly smooth heads. The owner can have placements of hot mix asphalt anything and everything on segments 5 and 6 of the he or she needs to perform new State Highway 130 central the most precise job that he Texas toll route south of Austin. needs to." Two identical pavers were used Speed of forward movein echelon to get a hot joint ment will impact the quality Within ProVAL, after data input, users may select or unselect the desired pavebetween the two lanes. The and evenness of the cut. "As ment profiles by their corresponding checkboxes. Selected profiles will be displayed on the chart. From this point on, you can view the profile, manipulate hot joint was specified by the long as the bid is all about the data, perform analyses, and produce reports owner and the contractor was production – that's the way paving 40 feet wide, with a 22-foot-pull outside and an 18all milling contractors make money these days, by the square foot pull on the inside, including a 6-foot inside shoulder and yard and tonnage that they achieve in a day – the machine 10-foot outside shoulder. has to run at a high rate of speed," Wiley said. "But very high The pavers were getting extremely smooth placements, speeds don't necessarily mean a high-quality cut. It's better for a milling contractor to run at a somewhat slower speed, but at says Jerry Jaeger, field manager for Industrial Asphalt, Austin. Specs required an IRI of 60 or below, but the pavers were a steady pace, 40 to 45 minutes an hour, and he still will have achieved the production he needs at the end of the day, but well below that threshold. "I don't think we would have got with a superior pattern." it with other pavers, but these were getting 20s and 30s IRI The faster you go, the worse the pattern gets. The rougher readings," Jaeger said. "I've seen that before with quarterthe texture, the harder it will be to maintain smooth grade mile stretches, but we're at 41 miles of continuous overlay. It's with the milling machine, he says. exceptional." "The IRIs we have been getting are unbelievable," says Brian Swift, superintendent for Industrial Asphalt. "We're getting anywhere from 26 to a 37, and the requirement is 60." Smoothness was being augmented by the paver automatic The next critical point in attaining smooth asphalt pavements control system utilizing 50-foot skis. Two skis were used on is the paving process. The theme here is don't stop. the 18-foot paver and one on the 22-foot paver. Begin by isolating the paver from the supply truck; that's At the same time, work was proceeding on the Circuit of done via religious use of the Roadtec material transfer vehicle Paver operations 10 October 2013 Better Roads RoadScience_BR1013.indd 10 9/30/13 3:40 PM

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