Hamm has rolled out a new compaction technology specifically designed for the sensitive task of asphalt joint compaction. When two lanes of asphalt are paved side-by-side, the "cold joint" (the seam where the fresh, hot mix meets the previously laid, cooled mix) is the weakest point in the road and prone to water infiltration and cracking. Traditional vibratory rollers use vertical impact to compact, which can shatter the aggregate at the joint or cause the mix to shift, creating a ridge. Hamm's new Oscillation system offers a solution.
Instead of using a single rotating eccentric weight to bounce the drum up and down (vibration), the Oscillation drum utilizes two opposing eccentric weights that rotate in a synchronized pattern. This cancels out vertical forces and generates a purely horizontal forward/backward shear force. The drum effectively "kneads" the asphalt horizontally like a baker working dough.
This horizontal force squeezes the asphalt mix into the voids of the cold joint seam without the damaging vertical impact. Because there is no bouncing, the drum remains in constant contact with the pavement, transferring 100% of the machine's weight to the surface. This "static weight" effect achieves high density without the risk of over-compaction or aggregate fracture.
Field trials on a German autobahn expansion project showed that the Oscillation roller achieved 99% density at the cold joint compared to 94% with standard vibration. Furthermore, because the oscillation energy is absorbed entirely by the pavement, the machine produces zero ground-borne vibration. This allows contractors to compact asphalt right next to sensitive infrastructure-like hospitals or historic bridges-where traditional vibration would normally be banned.
