The window for road paving in Canada is tight and every day counts whether it’s the spring start or the race to finish in the fall before winter sets in.
No one understands better than Canadian pavers that cold temperatures create problems with the mat cooling faster and shortening the time available for optimum compaction and density.
To avoid those mat cold spots, Bomag says its recently tweaked specialized pavers 652 and 662 with remix technology. The machines have been around since the 1990s but Henry Polk, Bomag product manager of paving, says they’ve been consistently tweaked over the years.
“More recently we changed the design of the augers which is really critical,” he says. “Before they were hand-made more or less, with the ribbon blades put on individually. Now we’ve designed them with bolt on ribbon blades so that if one is failing or needs to be changed you just replace it not the whole auger which could get pretty expensive.”
It’s those twin augers in the paver which continually churn the mix, he says, and keep the temperature consistent all the way through. As the mat flows out there are even temperatures across the board as it cools, which means fewer problems down the road because it resists water penetration and resulting frost heave.
The big issue, he says, is cost.
“These cost US$20,000 to $30,000 more than other pavers,” he says. “But you get more consistent quality and a longer season.”
Also, he adds, with more state road agencies setting temperature specifications read by a handheld thermal reader, the benefit of laying a mat which is consistently within spec pays off.
“If they don’t meet the specs, they get penalized and they have to go back and dig up that spot and relay it,” he says. “In some cases, the state agencies are giving bonuses for those that meet the specs. One of our customers paid for his paver investment within a summer through those bonuses.”
Indeed, Bomag has published a case study of a Minnesota paver using their CR652RX remix paver on a job with a temperature spec.
“If the temperature differential is less than 25 F (14 C) across the mat’s width every 150-ft (45.7-m) segment, we receive maximum bonus,” said Scott Heglund, paving supervisor for Duininck Inc. “If the differential is between 25 F to 50 F (14 C to 27 C), we receive regular pay, and if the differential exceeds 50 F (27 C), we receive a penalty.”
In all there were about 330 segments for each lane, where bonus or penalty could be assessed, he said. They system scored them a maximum bonus in every category making the cost differential insignificant on one job along.
The other advantage of constantly remixing in transport is that fillers like shingles and other waste products can be better added and ground to fine consistently to avoid “clumping,” Polk says.
Bomag’s Bill Reiken, a paving specialist, spends a lot of time here as the rep for Canada, and says several contractors have adopted the pavers because of the challenge faced by short seasons.
“Also, some contractors don’t have the plant for a continuous paver so they do truck exchange,” he says. “This paver has counter-rotating augers which keeps the mix temperature more constant and uses outboard spreaders with no centre box so you don’t get the segregation down the centre line.”
The critical tweak, he says, has been to change the auger design.
“If you do the maintenance right these pavers will spend less time in the shop that other models,” he says.
Whether it’s a shave and pave or a repair spot, Reiken says, the constituency of the mix and temperature control pays off.
“There are some trouble spots where they will only use a remix paver,” he says. “Because they know the results will be good. Also, for commercial work you can take a low-cost mix and get really good results with it.”