Traditional Terex paver
Many HIR contractors customize equipment in the recycling train to meet their own individual requirements. Some contractors employ a modified recycling agent/mixing/paving unit to lay the mix; whereas others use a free-floating screed attached to a heater/scarifying unit. Dustrol takes a different approach to paving the recycled material.
Dustrol has been perfecting its process for more than 30 years, and the contractor relies on a conventional Terex Mat Smoothness machine and paver to lay the mat. "We find we get a better final product by using the pick-up machine and paver," says Murphy. "By not tying it all together, we can modify the speed of the paver and adjust the screed settings to meet paving conditions."
Transferring the windrowed material to the paver for Dustrol's crew is the Terex MS2 Mat Smoothness machine. The MS2 attaches to and is maneuvered by the paver - eliminating the need for additional operators - and features three-point suspension with hydraulic front leveling. Wide 124-inch receiving tunnel and 60-inch asphalt elevator deliver more than ample throughput capacities to keep up with the recycling train. Direct hydrostatic conveyor drive and heavy-duty 0.5-inch-thick elevator flights maximize uptime.
Material was then efficiently transferred to the 14-ton receiving hopper of the Terex CR462 rubber track paver. Offering a maximum 28-footpaving width and 12-inch depth, the CR462 features exclusive Frame Raise and Three-Point Suspension Systems to improve mat quality and smoothness. The patented Smartrac System automatically maintains proper tensioning on the 18-inch-wide rubber tracks, which extends track and component life.
Dustrol equipped its paver with the Terex Stretch 20 electric screed, powered by a 34 kW generator. The Stretch 20 offers four-zone thermostat heat control. "We feel the electric screed gives more uniform heat across the screed bottom," says Hansen, which helps to improve mat quality.
Behind the paver, Dustrol employed a traditional three compactor rolling pattern to reach specified densities, which for the Turner Turnpike application were 92 percent of Gmm as determined from daily production.
A steel tandem vibratory roller served as the breakdown roller, while a rubber tire and second tandem vibrator roller served as the intermediate and finish rollers respectively. "The intermediate rubber tire roller was used as needed to achieve densities," comments Hansen.
Dustrol's full HIR recycling train achieved a production rate of 2 to 3 lane-miles per day on the I-44 Turner Turnpike application. After the HIR paving train finished its job, Haskell Lemon's crews topped the 40 lane miles of recycled road with a Nova-Chip overlay. Hansen estimates that the HIR process on I-44 saved the Turnpike 20 to 30 percent as compared to using a standard mill and fill process.
By employing a conventional paver as part of the HIR train, Dustrol's crews were able to deliver a smooth intermediate surface for the Nova-Chip overlay, which ultimately helped Haskell Lemon's crews achieve the 5-inch per-mile profilograph spec using a 0.2-inch blanking band and a maximum bump of 0.3 inches in 25 feet.
"We developed a smooth, non-stop paving process with the paver," explains Murphy. "This helped to meet the tough ride specs, which has been a determining factor for using a conventional paver as part of our process."