At a trade show recently, we came upon an arresting sight: Hundreds of pounds of dark black cold mix asphalt (CMA) road patching material, piled high in an open display box—but without the odor of petroleum solvents or the oily residue of typical cold mix. This product is U.S. Cold Patch.
With our interest piqued, we contacted a long-time user of U.S. Cold Patch, Glenn Akramoff, who recently took the position of interim maintenance manager in Covington, Wash., located south of Seattle (population 17,000 and 120 miles of road). Akramoff has been using U.S. Cold Patch to repair municipal pavements for nearly five years, almost as long as the product has been on the market.
Akramoff uses this product to fill potholes and cracks and for emergency repairs—even for the maintenance work he wouldn't attempt with other brands of CMA, such as “skin patching” to repair road delaminations. “In nearly 20 years of street maintenance this is only product I've found that works in very shallow holes,” he said. Akramoff concluded with a story: “Last December, when I was maintenance manager in Sammamish, Wash., and our road repair work shut down during the holidays, we had the contractors to come back to their sites daily to keep the potholes filled,” he said. “They used regular cold mix. On weekends, my crew would check the sites, and make repairs as needed with U.S. Cold Patch. Our patches held, and those made with regular cold mix did not—this was true even in potholes that contained both products. U.S. Cold Patch really is a permanent repair material.”
To learn more about this new product and about cold patch and potholes in general, we called John Ackerman, general manager of Everett, Wash.-based YK Products LLC, which manufactures U.S. Cold Patch.
Let's start with basic terms: hot asphalt and cold asphalt.
Hot mix asphalt, or HMA, is most widely used for road paving around the country. The asphalt is heated, mixed with aggregate, and put down by paving machines. When the asphalt cools, the pavement hardens. But hot mix often too cumbersome or too expensive for road maintenance work. For those jobs, repair crews use one of two kinds of CMA: cutback asphalt or emulsified asphalt. With cutbacks, liquid asphalt is blended with a petroleum solvent to keep it from solidifying. This is then mixed with the aggregate. With emulsions, liquid asphalt is milled into tiny droplets that are suspended in water and an emulsifying agent. This solution is used to coat the aggregate. With both methods, the concrete hardens and cures through evaporation.
So which is type of cold mix is U.S. Cold Patch?
Actually neither. It's an entirely new type of cold patch.
Can you describe the technology?
It was developed by two asphalt engineers who were seeking a new use for reclaimed asphalt pavement, or RAP. Some 20 million tons of RAP are disposed of in landfills every year. These engineers spent five years working on this project, and in the end they devised a way to reactivate the hardened asphalt in the crushed RAP without the use of cutbacks. This dry and granular mix of reprocessed RAP is the main ingredient of U.S. Cold Patch. When compacted, it hardens and adheres to the surrounding pavement. It's permanent. In most cases, you can pave over it right away. Compaction is the key—preferably with the wheel of a truck or car.
Is there a difference in the environmental impact of the various types of cold asphalt?
A big difference regarding environmental impact and worker safety. This is especially true with cutbacks. Most cold asphalts that I've seen are made with petroleum solvents, usually kerosene or naphtha—I'd estimate roughly a quart per bag. These solvents contain VOCs—volatile organic compounds—and hazardous air pollutants, which road workers breathe and that evaporate into the air or run off into soils and groundwater. Two pallets of bagged material contain about 20 gallons of these solvents, which is a significant pollutant. If a product works as well or better than competitive brands, costs about the same, but is significantly safer for workers and the environment, then I believe consumers will buy that product. This has been the response from municipal customers after they field-test U.S. Cold Patch.
You mentioned that U.S. Cold Patch is made from RAP. Is there RAP in other cold mixes?
Not in any competitive brands that I've seen. Every pallet of U.S. Cold Patch contains nearly three-quarters of a ton of RAP that has been diverted from landfills or used for other low-end applications such as base courses.
How about describing a drawback to your product?
Our greatest challenge is educating new users. Our product is dry and odorless, both of which are indications with other cold mixes that the product is old, and perhaps unusable. It's sometimes difficult for new users to believe that a product as dry as ours will compact and harden as well as it does.