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When it comes to compaction — whether it's soil or asphalt — many contractors rely on experience with similar materials to set amplitude and frequency, the number of passes and roller speed. Yet, a variety of factors can affect how quickly and efficiently density is achieved on a particular surface, including changes in ambient temperature or weather, moisture content in soil, mat temperature for asphalt, mix quality, and experience of the roller operator.

Manufacturers of large rollers have recently introduced drum and onboard control technologies designed to minimize the effect of such variables. The goal is to transform the compaction process into less of an art and more of a science.

Greater frequency plus a smart drum

High-frequency asphalt rollers have grown dramatically in popularity. Dale Starry, product manager at Ingersoll Rand, attributes this to an increase in average paving speeds. Higher frequencies (3,800 to 4,000 vpm) enable the rollers to maintain the same impacts per foot at faster rolling speeds. This in turn speeds up the entire paving process and, in some cases, can eliminate an extra roller on the job.

One of the challenges associated with higher frequency has been the potential for increased bearing wear in the drum. "The life of the eccentric bearings that support the unbalanced weight inside the drum is reduced by the factor of the speed of rotation," Starry says. "If it spins at 2,500 vpm, bearing life might be 10,000 hours. If it spins at 4,000 vpm, the life might be 2,000 hours."

In order to achieve acceptable bearing life, some manufacturers have been forced to reduce the load on the bearings by reducing amplitude. "That means that the high-frequency compactor can't compact layers as thick as a standard compactor of five years ago," Starry says.