The Benefits of Vibratory Compaction for Ultra-thin Lifts

Any good paving crew will tell you that compacting ultra-thin lifts — those typically an inch or less — comes with a unique set of challenges. There isn’t a lot of material for leveling, so mistakes on thin asphalt overlays are difficult (if not impossible) to correct. The thinner mat also cools more quickly, so compaction operators have to adequately keep up with the paver or risk damaging the surface. There’s essentially little to no room for error.

Another important factor when it comes to ultra-thin lifts is that many think amplitude becomes irrelevant, either because vibratory compactors simply exert too much force on the material, or the fact that a lot of ultra-thin overlay jobs include a non-vibration spec.

This is why paving contractors either static roll with their current double drum machines or supplement their fleet with single- or double-drum oscillation rollers. While either method is suitable for compacting ultra-thin lifts, there is another option: vibratory compaction — but it takes the right machine.

At Volvo, we’ve been hard at work designing double-drum vibratory compactors with an even wider range of amplitudes and frequencies. Our new DD128C asphalt compactor is a great example. It features an ultra-high frequency of 4800 vpm and drum amplitudes from a super-low 0.003″ up to a high of 0.030″. That’s the widest range of amplitudes on the market, allowing operators to dial it down to compact with vibration on ultra-thin lifts, or dial it up for deeper 4-inch (10 cm) lifts.

Amplitude setting three or four on the DD128C would be comparable to most compactor’s lowest amplitude setting — that essentially expands the adjustment range for the operator to fine-tune the low amplitude for ultra-thin lifts. When you utilize its auto-reversing eccentrics, you also have the best shot at laying mats with incredible smoothness.

What all this means is a paving contractor could utilize one double-drum machine for virtually any lift thickness instead of having to purchase or rent oscillation and/or vibratory compactors to take on a wider range of jobs.

Compactor Speed Impacts Thin Lift Performance

The paver speeds are typically increased when laying thin lifts, and the compactor needs to be capable of keeping pace. The challenge is that static rolling oftentimes requires additional passes to reach the target density, and oscillation frequencies are usually in the 2400-2500 vpm range (about half of the DD128C). In either scenario, the paver will likely have to travel slower to account for the compaction speeds, which compromises production.

In setting one on a Volvo DD128C, vibration frequency is fast enough to go 5.5 miles an hour and still maintain 10 impacts per foot, which is a best practice. The Volvo DD128C vibratory compactor has the potential to eliminate passes so it can keep up with the paver — in turn, improving productivity while maintaining or even improving the quality of the finished surface.

Running your double drum compactors in static mode or supplementing your fleet with oscillation compactors are both fine options — they’re just no longer your only options. You may be able to reduce fleet size with a vibratory compactor like a Volvo DD128C. It’s worth talking to your local Volvo dealer to determine if it’s a good fit for the types of paving jobs your company takes on.

by Justin Zupanc