Investing in Cold In-Place Recycling

Created: October 14, 2010

Canadian road agencies are looking for cost-effective, quality alternative to mill-and-fill rehabilitation.

To cold-recycle a road costs about 60% of what it will cost to do a mill-and-overlay. That's because the recycled asphalt does not have to be hauled back to the hot plant, recycled and hauled back out...
To cold-recycle a road costs about 60% of what it will cost to do a mill-and-overlay. That's because the recycled asphalt does not have to be hauled back to the hot plant, recycled and hauled back out to the road.
Leading off Cruickshank's recycling train is a Roadtec RX-900 milling machine, which feeds recycled asphalt pavement (RAP) directly into a Roadtec RT-500 Mixing Trailer. After a full mixing cycle, the...
Leading off Cruickshank's recycling train is a Roadtec RX-900 milling machine, which feeds recycled asphalt pavement (RAP) directly into a Roadtec RT-500 Mixing Trailer. After a full mixing cycle, the rejuvenated RAP is discharged onto the roadway in a windrow. A Carlson windrow pickup machine feeds RAP back into a RP 195 paver.

"Environmentally speaking, cold in-place recycling is the way to go," says Cruickshank. "Quite often, when you have environmental solutions, they are more expensive than the conventional method. But in this case, the environmentally friendly solution is lower in cost than the mill-and-pave method of reconstruction."

CIR in action

Cruickshank won its first project on Highway 140 north of Port Colborne, Ontario. It was a 5.5-kilometer-long project with about 45,000 square meters of recycling work. The Roadtec RX 900 cut 100 millimeters deep (3.9 inches), and worked along at about 260 to 270 tons per hour.

With the Roadtec train, Cruickshank can control the gradation of the RAP being recycled into the pugmill. "We have a crusher and a screen, and the screen ensures that the material meets the 37.5 millimeter size," says Semley. "If we have any oversize material, the crusher reduces that further."

"When you are working for the province it is mandatory to control the gradation," says Cruickshank. "Not every one of the cold in-place recycling systems allows for that."

Another advantage of the Roadtec train is that it adds emulsion or liquid binder based on mass, or weight, of the reclaimed material.

"Others measure their liquid additive based on volumetrics, and that does not meet the specs from the Ministry of Transportation in Ontario," says Semley. "Others calculate the amount of liquid that they add based on the theoretical volume. Ours is a real-world measurement based on the weight of material across the weigh bridge. That meets the spec from the MTO."

Semley said the Port Colborne project took just eight working days. Cruickshank used a 1-meter-wide milling machine working in echelon with the big RX 900 mill. The smaller machine windrowed RAP over in front of the larger one, which picked it up for processing. It was a two-lane road that required two passes with the two milling machines.

The crew does face a learning curve if they are inexperienced with CIR, says Semley. "By the end of the Port Colborne job we were comfortable with the process," he says.

The second CIR project for Cruickshank was a 55,000-square-meter job on Aviation Parkway in Ottawa, Ontario. The width of the project varied up to 16 meters wide, and the depths of cutting varied up to 175 mm deep. The contractor crushed RAP to the 37.5 mm spec and added liquid binder at a rate varying from 1.5 to 2.8 % by weight.

All CIR work in Canada is done by the low-bid system, and Semley is confident that they can keep the train working.

"We got started in mid-July, a late start," says Semley. "We expect to be busy for the rest of the season."