BOMAG has unveiled an advanced compaction technology for its BW 174 asphalt rollers that automatically switches between oscillation and vibration modes to protect bridge decks during road surfacing. Compacting asphalt on bridges presents a unique engineering paradox: the asphalt requires high-energy vibration to achieve density, but the resulting resonant frequency can damage the bridge's structural concrete and expansion joints. BOMAG's solution utilizes a dual-mode drum architecture that adapts to the substrate in real-time.
The system utilizes the machine's existing TerraControl module coupled with a structural sensitivity sensor mounted on the drum frame. As the roller drives onto a bridge deck, the sensor monitors the feedback frequency from the drum impacting the pavement. If the sensor detects that the bridge structure is beginning to resonate-a condition that can cause micro-cracking in the concrete-the system instantly disables the vertical vibratory eccentric weights and switches to horizontal oscillation.
In oscillation mode, the drum generates a forward/backward shear force rather than a vertical impact. This kneading action compacts the asphalt efficiently without transmitting damaging energy into the bridge girders. The transition is seamless, occurring within a single revolution of the drum.
Furthermore, the system records the compaction data and location via GPS. This creates a "digital proof" for the bridge owner, verifying that the structural protection protocols were followed. In a recent highway rehabilitation project over a steel-girder bridge, the BOMAG system allowed contractors to achieve 98% Marshall density on the wearing course without exceeding the safe vibration limits for the aging structure, eliminating the need for static rolling only which typically results in lower quality asphalt finishes.
