Faster Compaction, Wider Applications Possible With Oscillation Technology
January 2004 – Oscillation compaction technology – new to North America – is allowing faster compaction of asphalt, with fewer rollers nneeded, asphalt contractors are finding.
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Unique, nonaggressive Oscillation compaction from Hamm Compaction Division, Wirtgen Group, is available in North America via the new Hamm HD O90V oscillatory/vibratory roller, introduced to the industry at World of Asphalt 2003 in Nashville. The designation HD O90V signifies a hybrid roller of the Hamm HD 90 platform, in which the front has a conventional vibratory drum, and the rear incorporates the revolutionary Oscillation technology. |
Unlike traditional vibratory compactors that achieve compaction by "bouncing" the drum on the ground, Hamm's unique Oscillation technology ensures that the roller drums maintain constant contact with the ground for faster, more effective compaction.
In the oscillation drum, two eccentric masses turning in the same direction cause a movement around the drum axle. The movement changes its direction of effect during one turn so it generates an oscillating or rocking movement of the drum. Horizontal forces are transmitted from the drum into the pavement. The result is better compaction in fewer passes, with less vibration-related wear and tear on operators and surroundings.
In 2003, a contractor used a Hamm HD O90V to compact a Superpave leveling course on Kansas 96 near Wichita. This project involved a 45-mm (1.7-inch) Superpave leveling course, with PG 70-28 polymer-modified liquid asphalt binder with 1-inch top-sized aggregate. This intermediate course ultimately would be topped with a 25 mm PG-graded wearing course.
Previously, breakdown compaction had been accomplished by a 24,910 lb., double-drum articulated roller, with intermediate compaction by a pneumatic roller, and finish compaction with another 24,910-lb articulated roller.
However, on this project, the nonaggressive Oscillation compaction was achieving better compaction numbers, faster, than the pneumatic and finish rollers combined. That prompted a pavement technician to observe that the HD O90V could take the place of two compactors.
Compaction numbers were being checked with a Troxler 3411B density gauge. Numbers attained with the conventional, three-unit compaction train were 91 to 92.5 percent maximum. But with the HD O90V, compaction from 91 to 94.5 percent was being achieved with just two rollers.
"Non-aggressive, oscillatory compaction can achieve improved densities
without breaking aggregate in the mix," said Mark Blessen, Wirtgen
America regional sales manager. "It results in a smoother ride surface,
because the drum never leaves the mat. Improved centerline and edge joint
densities are obtained with Oscillation compaction. And one roller can
eliminate two on this job."
Also, nonaggressive oscillation compaction makes possible use of HMA to
overlay bridge decks, as happened last year in Norway.
Asphalt contractors have long coveted the bridge resurfacing market, but have been stymied by specs which preclude use of vibratory compaction and its fast rate of compaction. For example, to avoid structural damage to bridge structures and base courses, Norwegian law forbids the use of vibratory compaction on bridge surfaces.
Traditionally, this is a job that has been charged to static or dead
weight rollers. But on the Norway bridge decks, Hamm Oscillation technology
was achieving a density of 97 percent in four passes, the contractor reported.
Compaction was achieved faster, using less fuel, while safeguarding the
structure of the bridge.
More information about Oscillation technology, or the HD
O90V, is available from Hamm Compaction Div., Wirtgen America,
Inc., http://www.wirtgengroup.com.
BACKGROUNDER
Wirtgen America, Inc., Nashville, is the North American arm of the Wirtgen
Group, the single-source marketer of the world's most technologically
advanced lines of asphalt reclaiming and recycling equipment from Wirtgen,
asphalt and soil compactors from Hamm Compaction Division, and U.S.-sourced
asphalt pavers from Vögele America Inc.
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