Wirtgen Group has announced the integration of advanced 3D grade control technology into its WR 240i cold recyclers, bringing millimeter-accurate automation to large-scale road rehabilitation. Cold recycling involves pulverizing the existing damaged asphalt and underlying base material, mixing it with a binding agent, and laying it back down as a new stabilized base. Historically, achieving the correct elevation and cross-slope required surveyors to install a physical string-line along the shoulder, which the machine's sonic sensors would follow. This setup is labor-intensive and easily disrupted by site traffic.
Wirtgen's new 3D system replaces the string-line with a robotic total station positioned off the machine. The total station continuously tracks a 3D prism mounted on the recycler's rotor housing. This position data is fed into the machine's onboard computer, which compares the current rotor elevation against the project's digital terrain model.
To manage transitions where the total station's line of sight is blocked-such as under bridges or heavy tree lines-the system integrates dual sonic tracers on the side of the rotor. These tracers bounce sound waves off the existing pavement edge to maintain a relative grade reference. The machine's control module seamlessly blends the 3D total station data with the sonic tracer data, automatically adjusting the rotor depth via hydraulic cylinders up to 10 times per second.
During a recent 8-mile highway rehabilitation project, the automated cold recycler maintained a strict 2-centimeter vertical tolerance without a single string-line stake in the ground. This eliminated days of pre-project surveying and allowed the contractor to continuously reclaim the road base at a rate of 2,000 square meters per hour.
