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Developing Cold Mix

The development of cold mix asphalt has provided a new solution for road and pavement repairs in Canada.

The development of cold mix asphalt has provided a new solution for road and pavement repairs in Canada. Cold mix asphalt allows for repair work to be done in all temperatures without worrying about being able to keep the asphalt hot during transport from asphalt plant to job site.

While several equipment manufacturers have worked to develop paving plants that process cold mix asphalt, allowing for larger paving projects to be completed using just the cold mix material, portable cold mix solutions are also being developed.

In B.C., Mainroad Maintenance Products LP, located in the Vancouver suburb of Surrey, is marketing a polymer-modified cold asphalt called EZ Street that, it claims, is guaranteed to permanently repair potholes, utility cuts, overlays and edge repairs in asphalt or concrete. 

The EZ Street cold asphalt mixes come in two versions: Regular EZ Street, which has regular diesel as one of its ingredients, and Bioblends EZ Street, which is made with 100 per cent renewable resources and selected recycled materials.

EZ Street cold asphalt can be applied when air temperatures are between -18 C and 38 C. “But EZ Street will be most pliable, workable and able to be compacted at air temperatures between10 C and 32 C,” Hoare says. “In the winter, you can warm the material before you apply it, although you must take care the temperature of the material temperature doesn’t go above 50 C.”

Hoare says that, to ensure best performance, EZ Street should be applied and compacted in two-inch maximum lifts.

“Compacting the material using a vibratory steel wheel roller will give you the best results,” he says. “But wheel rolling using steel wheel or pneumatic rollers, or  compactor plates, will also work. And over-compacting is rarely a problem.”

While EZ Street has been primarily used for smaller projects such as pothole repair, utility pole installation and pedestrian pathways, there are larger installations that are also finding success in laying cold mix asphalt as a paving solution.

For example, Bowen Island, a small municipality of 3,500 people near Vancouver, recently used Bioblends EZ Street as paving overlay on a stretch of road 50 metres long by five metres wide.

“We’ve been using EZ Street for about the last four years,” says public works foreman Kevin Toews. “In addition to paving overlay, we use it to fill potholes and to patch road shoulders. Application is straightforward. We shovel it from the truck onto the asphalt as an overlay, compact it, then throw sand on it and it’s ready to drive on almost immediately.”

One of the reasons why Toews has chosen to use a cold-mix asphalt product is that he finds the versatility of the product to be valuable for his operation.

“It works on both flat and steep grades and it stands up to any weather conditions,” he says. “We use about five truckloads of it per year.”

The B.C. Ministry of Transportation and Infrastructure (MOTI), which oversees an extensive road paving, repaving and maintenance program, used EZ Street’s regular cold mix asphalt on a mill and pave project on a 1.4-kilometre stretch of well-used Highway 99 that runs south from Vancouver to one of the busiest U.S. border crossings in Canada. The original conventional hot-mix asphalt surface had suffered severe alligator cracking.

“We heard about of the benefits of EZ Street asphalt, so we completed a test section,” says MOTI operations manager Thomas Chun. “To date, the cold mix asphalt has performed as we expected, in that it has held together well. There are some settlements, but that is base-related and we were aware of those. The ministry will continue to monitor this segment of roadway to determine the long-term impact.”

While some paving contractors remain skeptical about the use of cold mix asphalt, the results being found on Canada's west coast are providing some good reasons why cold mix asphalt could emerge as an effective solution for road paving and repair.