Asphalt movement in the hopper of a traditional slat paver is from front to rear. However, the CR662RM’s counter-rotating augers draw down and remix asphalt from all areas of the hopper. The variable-pitch design of the augers aggressively reblends 100% of the asphalt prior to delivering it to the spreading augers.
Beyond reblending capabilities, Rieken offers an additional benefit of the variable-pitch auger design and spread auger drive system of the CR662RM over traditional slat pavers with a center gearbox spreading auger design.
“The variable-pitch augers do not fracture the aggregate like the slat chains can,” he says. “This fractured stone typically falls underneath the center gearbox drive of most pavers, resulting in centerline segregation.”
Since there is no aggregate fracture and the spreading augers are driven by outboard drive motors, “the CR662RM’s design eliminates the possibility of this type of segregation.”
The end result for the contractors is a more homogeneous blend of asphalt delivered to the spreading augers, which is void of both material and thermal segregation. “The MTQ has workers on the job with thermal imaging cameras to ensure that the mat has a uniform temperature reading across the width of the mat,” mentions Lefebvre.
A paving superintendent from one project contractor adds that the MTQ is looking for the hotter red and orange temperature readings in the camera, and the readings have been very consistent behind the screed.
Full width, hot joint
What makes this uniform temperature accomplishment all the more impressive is the width at which the crews are paving. Each paver is equipped with a Terex Fastach screed built to pave two traffic lanes plus the small inside shoulder in one pull.
“Each contractor has enough screed sections to pave up to 32.8 feet wide,” says Lefebvre. Currently, the contractors are paving the two 13.8-foot travel lanes and one 2.6-foot small shoulder in a single pass, for a total paving width of 30.2 feet.
The Fastach screed comes with a standard 10-foot paving width and wide, 34-inch screed bottoms to increase mat smoothness. Screed extensions offer a unique pin-lock attachment design for quick installation and are available in 6-, 12-, 24-, 36- and 60-inch widths to meet a wide range of paving applications. The main screed and extensions, excluding the 6 inch and 24 inch slopeable, offer up to 3,000 vpm vibration to provide initial asphalt consolidation.
The 24-inch slopeable extension allows crews to place crowns in the road where required. The screeds paving on Autoroute 30 have two slopeable extensions, allowing crews to place a crown on either side of the paver for the small shoulder, depending on what direction the paver is paving. The main, 10-foot screed section of the Fastach provides the crown in the center travel lanes. The screed comes standard with power crown control with crown capabilities ranging from 3 inches positive to -1 inch.
With its 260-hp diesel engine and high tractive effort rubber track drive system, the CR662RM delivers the power and traction required to efficiently pave at the 30.2-foot width.
“The screed configuration includes six oil-fired burners to provide initial warm-up for the screed bottoms,” says Rieken. “The screed is also ballasted for excellent ground contact pressure to deliver the required ride smoothness.”
Following closely behind the mainline paver, the 8-foot Terex CR362 rubber track paver is used to pave the 8.2-foot-wide shoulder. By paving in tandem, crews have a hot joint to compact, which offers high quality joint construction. “Since the mainline paver is paving at full width, the joint is not in the travel lanes, which is what the MTQ prefers,” says Lefebvre. Rieken further explains, “The joint is typically where the first signs of failure will develop, so having the joint in the non-traveling lane should make it last much longer.”
With paving operations rapidly coming to an end, all quality and smoothness reports from the field have been positive. The combination of continuous paving, the CR662RM paver’s variable-pitch counter-rotating augers and full-width paving with the Fastach screed have resulted in a road surface void of segregation and without joints in the traffic lanes.