Better Roads Staff
Unlike other live-bottom units that push the material through a gravity-held end gate that restricts flow, “the door on the back of this guy opens up and the material can flow out very quickly,” says Benjamin Boelter, HiWay’s engineering manager. “It usually takes only one revolution – technically half-a-revolution – of the belt to clean the material out of there. This will unload quicker than a dump body, if you lift the dump body all the way up and put it all the way back down again.”
The body is insulated and tarped to keep material temperatures constant, “and how far the unit hangs out in the back is designed so that it dumps better into a paver,” points out Boelter, who says the ability of the Asphalt Transporter to maintain the integrity of the mix reduces the need to rework the material at the paver. “It does, understanding that in certain applications there are requirements by the state to have a re-blending machine anyway.”
On the very week Boelter spoke with Better Roads, he and his colleagues at the HiWay plant in Cedar Rapids, Iowa were visited by an asphalt contractor from the Northeast, on hand to watch a double-digit Asphalt Transporter order roll off the assembly line. Production aside, safety is a key catalyst for the customer, whose crews are working in rough terrain and facing tipping hazards with dump trucks, says Boelter.
A Little Help, Please
As bewildering as trucking can be for any paving contractor, the material quality problem – or at least a solution to the problem – doesn’t just lie in the hauling equipment, says Rieken.
“If we’re going to get serious about material temperature differential and material segregation, we’re going to have variable-pitch, counter-rotating augers in our paver hoppers. Instead of just conveying material to the back, you’re actually pulling from the full length of the hopper and getting a very aggressive re-blending process, instead of just transferring. It’ll just eat those cold clumps up,” he says. “When you’ve got the long hauls and the cold ambient days, if you have augers it’ll just take all those cold clumps away and you’ll have a nice uniform mix materially and temperature that you can still put down.”
It’s an evolution, points out Sunkenberg. “Windrow paving in a lot of ways is the original material transfer vehicle, on just such a smaller scale,” he says. Having a surge of material – in the case of windrow paving already on the roadway – allows the crew to avoid paver stops, running at a consistent 30 feet per minute all day long if desired. Where cooler temperatures or severe weather is an issue, a material transfer vehicle answers the need by placing a surge of material into re-mixing apparatus ahead of the paver. This accomplishes two objectives – eliminating temperature or material segregation and providing for non-stop paving.
“And those,” says Sunkenberg, “are the things you are most concerned about with trucking.”
A Multitasking Paver
Segregation in the mix may occur during the hauling process, but answers to the problem may lie at the paving train, including in the paver itself.
Some contractors working with mixes particularly prone to breaking up, such as Stone Matrix Asphalt, are finding success in reducing amounts of segregated material by using Remix Anti-Segregation System pavers, reports manufacturer Terex Roadbuilding.
A Remix paver offers re-blending capabilities at the last stage in the paving process by replacing traditional slat conveyors in the hopper with two sets of counter-rotating augers. It is the combination of the augers pulling uniformly from all areas of the hopper – rather than the front-to-rear pulling motion of slat conveyors – and the re-blending action which helps reduce both thermal and material segregation.
The Remix system is available on highway-class Terex pavers. Remix pavers can receive material directly from trucks and trailers, or can be used in conjunction with material transfer devices.
What’s a poor driver to do
They are often the forgotten ones . . . until, of course, they’re nowhere to be found when the paving crew needs more mix. Then, everybody from the superintendent in the fancy pickup right down to the rake jockey behind the screed is screaming about them.
They are the truck drivers – admittedly for many paving contractors the most misunderstood and frustrating “contributors” to the paving job. Normally, we’d refer to everyone who plays a role as “members” of the team – but often those truckers aren’t even that officially. A good number of road builders job out their trucking needs to subcontractors, often independent owner-operators in essence competing with the truck in front or behind them in line ahead of the paving train.
Even paving equipment experts – usually focused on either the plant or the jobsite end of the equation – have historically tended to skip over the hauling part that links the two ends.
Fortunately, that is changing.
The very first page of text in Volvo Construction Equipment’s Paving and Compaction Guide, Best Practices, is devoted to Truck Driver Responsibilities. Primarily, these are to properly load the truck at the plant and to maintain consistent delivery of the hot mix – in a homogenous mass avoiding segregation – to the material transfer vehicle, paver or windrow at the jobsite. Says Volvo, the Best Practices for doing so:
MORE FROM Highway Contractor
- Sydney uses water curtains to alert drivers to stop (VIDEO)806 Views
- Florida’s Red Light Camera Game: G R E E N orange R E D289 Views
- Big four cellphone companies jointly launch anti-texting campaign267 Views
- Acceptance of connected vehicles depends on cost, LaHood says265 Views
- Cities rethink transportation due to drop in young drivers260 Views