The lead compactor, usually a double-drum vibratory steel roller, working close behind the screed while the mat is at its hottest. It achieves most of the density gain, taking the mat from the screed's 80 percent or so to within a couple of points of target. Breakdown rolling has to happen before the mix stiffens, so the operator watches mat temperature and the paver's pace rather than the clock.
Breakdown roller's falling behind, get him up on the screed, he's rolling 220-degree mat back there.
Also heard as
- breakdown
- lead roller
Related terms
Rolling pattern
The planned number, order and coverage of roller passes needed to reach density across the full mat.
Pneumatic roller
A rubber-tired roller whose offset tires knead the mat, closing surface voids during intermediate rolling.
Tender mix
Mix that shoves and moves under the rollers instead of compacting, often within a certain temperature range.
Density
How tightly a compacted asphalt layer is packed, reported as a percentage of its maximum theoretical density.