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There’s no question that density specifications on today’s high-production paving projects are getting harder and harder to achieve. Strict smoothness requirements, tight project timelines, variations in mix quality, changing weather conditions and various other factors can all seem to conspire against you. Your ability to overcome these obstacles and still meet the numbers can mean the difference between getting the bonus or incurring a penalty upon completion.

High-frequency vibratory rollers have emerged as an important weapon in the fight to achieve specs and still maintain the necessary production rates. In fact, they often set the pace on high-tonnage projects.

“We pave depending on the speed of the rollers,” says Rick Ricker, paving specialist at P.J. Keating Co., Lunenburg, MA, and a trainer with Team Paving Consulting. “If I’m going into battle, I want to know there’s a good chance I am going to get maximum speed out of my whole [paving] train... With the high frequency, if I’m having a good day and it’s going well, I can max out the equipment and get my production.”

Staying within the envelope

When compacting hot-mix asphalt, there is a limited temperature envelope during which the asphalt maintains a certain amount of pliability, notes Bruce Monical, marketing manager, Hamm Compaction Division, Wirtgen America. If the paver is moving fast, and the rollers can’t keep up, you lose your window of opportunity to effectively achieve density.

“It all boils down to time and temperature,” Ricker agrees. “The sooner we can get to the mix - the hotter it is - we’re going to achieve a greater density with that material.”