Oscillation Conquers Changed Density Specs

A Columbus, OH asphalt paving and pavement maintenance firm is using exclusive Hamm oscillation compaction technology to tackle jobs that are difficult with conventional compaction.

And it's being driven by the City of Columbus' shift to density specifications on asphalt paving projects: meet the new density specs without excessive compaction and disruption to thin lifts.

Decker Construction Co. prides itself on its quality asphalt pavements, and is a recurrent winner of quality pavement awards presented by Flexible Pavements of Ohio, the state asphalt association. The firm uses four paving crews and four stone crews, on jobs that range from large driveways, tennis courts, commercial parking lots, private roadways, public streets and airport runways. And its two Hamm HD O90V oscillation rollers help make it possible.

"We have used our Hamm oscillation rollers through three seasons," says Fritz Smith, vice president, Decker Construction Co., Columbus. "We acquired them primarily because the City of Columbus changed its specifications, and went to a density spec for the surfaces of all newly constructed city streets for subdivisions and new housing. We had a tough time getting compaction with the standard roller design, so we changed to the oscillation rollers, which do a much better job."

The switch has done more than meet specs; it's enabled Decker to reduce the number of rollers on a job. "The HD O90Vs are more efficient," Smith says. "We've eliminated a roller off the roller train, and have changed our whole way of thinking about the roller issue."

What is oscillation compaction?

Hamm's unique, non-aggressive oscillation technology is changing the way contractors work in North America. The oscillation technology compacts with a gentle rocking motion, not a vertical pounding, and can be a powerful new tool for boosting asphalt paving productivity and profits.

Instead of vibrating straight up and down, the Hamm oscillatory design gives the drum a horizontal or "rocking" force which keeps the drum in contact with the mat.

Hamm oscillation technology attains very high compaction numbers with minimal passes and no shattering of aggregate. And as Decker Construction found, it often permits contractors to remove one or more rollers from a job.

"I've been here 25 years, and have watched the whole operation," says Bill Snoke, asphalt superintendent. "The Hamm rollers are our preferred weapon of choice. To reach our density spec, we usually can get it in one pass. It cut our fuel use almost a third from what we were using before. It's really made a difference. Its user friendly and you can see really well out of the cab. It's probably our most asked-for piece of equipment by the operators."

The HD O90V rollers were useful on a recent airport job, where 98 percent compaction was required on a runway. "We were reaching the spec with our double-drum rollers, but they weren't as efficient," says Jonathan Apple, project manager. "The Hamm rollers got density in fewer passes, and with a lot less fuel and water usage. We were able to run five rollers instead of six."

"With the old roller, we might have had to hit it with two to four passes," Snoke says. "With the Hamms we can cut back to one pass. They speed everything up."

The rollers have also precipitated a change in how Decker's subdivision streets are compacted. "We were running a three-wheeler up front," Snoke says. "We are now running the Hamms up front, following a meeting we went to earlier this year that pointed out that the hotter you hit it, the better it is. We've always said that, but it's hard to get that into the operators' heads."

The smoothness of the suburban mats also impressed Snoke. "You don't have bumps like you do with a three-wheeler," he says. "We were using three rollers, and now we use two. It means you can cut down on labor expenses."

Change in city specs