One of the primary uses of cold patch is filling potholes, so it is also called “pothole patch.” The product can also be used to construct sidewalks, fill utility cuts, and repair driveways, ramps, bridges, and parking lots.
Traditional Patching Material
The following products are currently used to patch potholes:
- Hot mix asphalt (HMA) is made of asphalt and aggregate. The asphalt hardens when it cools.
- Cold patch is made of asphalt, aggregate, and a solvent.
- “High performance” cold patch is made of a higher grade of asphalt, aggregate, and various additives such as fibers and proprietary solvents. It costs more than the previous two products, but lasts longer.
Recycled-Shingle Cold Patch
Recycled-shingle (R-S) cold patch can be made with either manufacturing scrap or old tear-off roofing shingles. A company that has sold R-S cold patch outside California stated that if manufacturing scrap is used, the patch is comprised of approximately 25 percent dry roofing material and 75 percent aggregate. If tear-offs are used, it is composed of approximately 25 percent dry roofing material, 3 percent solvents, and 72 percent aggregate. The patch could use virgin aggregate or reclaimed aggregate, which is obtained from crushing asphalt pavement.
The benefits of using recycled-shingle cold patch include the following:
Improved Pavement Performance
According to field tests (see “Testing,” below), R-S cold patch behaves like a “high-performance” patch, outlasting HMA and traditional cold mixes. The fiberglass and/or cellulose fibers in the shingles apparently add to the structural integrity of the patch.
Possible Economic Savings
Although the initial cost of R-S cold patch is usually higher than HMA and traditional cold patch, the overall cost may be lower due to longer life and decreased maintenance costs. When compared to other high performance patches, the R-S cold patch usually costs less.
Ease of Use
R-S cold patch is easier to use than traditional patches in the following ways:
- Lighter weight. It has a lower weight-to-volume ratio, so it is easier to handle.
- No equipment needed. Just fill the crack or pothole and tamp down with a shovel or drive over it.
- Time flexibility. It doesn’t harden as quickly as HMA, so there’s no hurry to use it. After applying, traffic can be allowed over the area immediately.
Landfill Space Savings
The amount of asphalt roofing shingles landfilled in California is estimated at 1.2 million tons per year, or about 3 percent of the waste stream.
The petroleum used to produce asphalt binders is a nonrenewable resource. All the asphalt needed in the patch can be supplied by the shingles; the mineral filler in the shingles supplies some of the smaller aggregates needed. If reclaimed aggregate is used, there are further savings of urban quarry resources.
The shingles should be ground and screened to 1/4″-minus, and mixed with the aggregates. If the shingles used are tear-offs, then a solvent is added to rejuvenate the old, oxidized asphalt.
In the early 1990s, a company called ReClaim was producing “RePave” R-S cold patch. A number of public works agencies in the U.S. field tested it and approved its use, including the following:
New Jersey Department of Transportation
Tested RePave for potholes in 1992. Results were promising; the patches lasted at least 18 months.
Borough of Haddonfield, New Jersey
The borough of Haddonfield applied RePave to potholes in 10 areas and monitored for one year. It performed better than most cold patch.
Hammonton, New Jersey
In 1994, the South Jersey Resource Conservation and Development Council in Hammonton used some donated RePave for a 3Ã¢Â?™ x 40Ã¢Â?Ëœ x 3″ sidewalk at a park. The product was easily applied by unskilled labor, on a gravel base with plywood siding. The council was interested in purchasing more product. As of 1997, the sidewalk is still in good shape.
Union County Public Works
Union County, New Jersey tested RePave on potholes and found it to be comparable to other high-performance cold mixes.
City of Bayonne, New Jersey
Tested RePave on potholes. It “worked well.” The R-S patch could be applied by unskilled personnel, and the potholes are still filled after at least two years.
Washington State DOT
RePave performed “satisfactorily” when tested by the Washington State Department of Transportation (DOT). Their new products committee recommended DOT approval.
Placer County Public Works
During the fall of 1997, the Placer County Public Works Maintenance Department applied a trial sample of R-S cold patch in potholes on county-maintained roads. Department staff is very pleased with its performance, and is interested in finding a supplier.
One key to opening California markets for R-S cold patch is to have the product tested by the Caltrans maintenance department. Caltrans’ testing of new road products adds a high level of confidence to a product or method.
For Caltrans to allow pothole patch with ground shingles, the product first must be sent to the following Caltrans department, with the appropriate forms:
New Products Coordinator
New Products Evaluation Program
Caltrans Office of Materials Engineering and Testing
P. O. Box 19128, MS #5
Sacramento, CA 95819-0128
The new products coordinator may pass the sample to the Caltrans maintenance department for field testing. If the product passes, it would then be allowed in Caltrans maintenance projects, and local public works departments would have more confidence in purchasing it.
Sources for R-S Cold Patch
To CalRecycle staff’s knowledge, there is currently only one manufacturer of R-S cold patch:
Gardner Asphalt Corp.
P. O. Box 5449
Tampa, FL 33675-5449
Gardner’s RePave is available to homeowners via Home Depot stores throughout California, except in Los Angeles County and Orange County. Ask for the SKU (stock keeping unit) number HD 932-314. It costs about $10 for a 3.5-gallon container.
CalRecycle has published a series of fact sheets, case studies, and resource lists on construction and demolition recycling. The are available on line via the CalRecycle’s online publications catalog, which includes a C&D section. From the catalog you may also order hard copies by e-mail or phone.