"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.