Sunday, 21 December 2014

Markets for Recycling Asphalt Shingles

Markets
Several potential markets exist for asphalt shingles. These include:
  • hot mix asphalt
  • cold patch
  • dust control on rural roads
  • temporary roads or driveways
  • aggregate road base
  • new shingles
  • fuel

Listed below is a description of each market and some of the benefits that may be derived from using recycled asphalt shingles (RAS).
Hot-Mix Asphalt (HMA)
This is the largest current market for RAS.There are several benefits which can be derived from using RAS. These include:
  1. Reduced demand on virgin asphalt cement
  2. Reduced demand on aggregate
  3. Improved properties of HMA pavement

The added asphalt cement decreases the demand for virgin asphalt cement. This has several benefits. Primarily, an economic advantage to the producers of HMA. Cutbacks from shingle factories can be ground up and immediately be added to the HMA process,or regenerated with rejuvenating chemicals prior to the HMA process.[Chelsea Center Technical Report #26] HMA requires certain gradations of aggregate.The ceramics in the shingles provide a source of aggregate, reducing the demand for mined aggregate. Certain properties of asphalt pavement have been shown to improve with the addition of RAS. These include rutting and cracking resistance [Evaluation of Roofing Shingles In HMA].It is suspected that the added mineral fillers and organic fibers help reinforce the matrix.

Cold Patch
The use of RAS as cold patch is a practice that has been employed for years. It has been used in New Jersey, Washington, and California as well as the city of Chicago. Advantages to using cold patch comprised of RAS include the following:
  • Patches have a longer life compared to other patch materials. This is likely due to the fibers from the felts or fiberglass in shingles.
  • The patch material is very easy to apply.A pothole is simply filled approximately an inch over grade. No equipment is needed as the patch may be compressed by vehicle traffic. The patch is also less dense than other materials, making it easier to haul.
  • The RAS cold patch material can be stored longer because it does not "clump" as quickly as other materials [CIWMB], [Roofing Shingles and Toner in Asphalt Pavement]
Dust Control on Rural Roads
Recycled asphalt shingles may be ground and mixed into the gravel used to cover rural, unpaved roads. The mixture leads to several improvements in these rural roads, including:
  • Dust is minimized. An Iowa DOT ["Let Me Shingle Your Roadway"] study showed little or not dust for two years on a rural road.
  • Reduced loss of gravel into side ditches.
  • Vehicle noise is reduced.
  • The roads have a longer life and require less maintenance. The study conducted by the Iowa DOT noted that the road performed well for at least two years.
Temporary Roads or Driveways
RAS has been used in temporary roads, driveways, or parking lot surfaces. RAS is typically ground to 1/4 inch and passed under a magnetic separator in order to sufficiently remove all nails. The processed shingles are spread and compacted for an easily installed surface. In Altus, OK, RAS was mixed with RAP to create a parking lot surface.
Aggregate Base
Little research has been conducted into this market, but shingles have been used as part of the sub-base in road construction. Processed shingles may be blended with recycled asphalt pavement and concrete. It is suspected that the addition of RAS may improve the compaction of the sub-base [CIWMB ].
New Roofing Shingles
A report prepared for the U.S. Department of Energy showed that the addition of up to 20% of recycled shingles did not affect the production of new shingles. They showed significant energy savings in using RAS.[See Technical Reports]
Fuel
The recovery of the BTU value of waste shingles is an established market in Europe. Only recently has the concept been applied in the United States. It is very limited, however, because of concerns over air pollution.

 

Last Updated: ( Friday, 12 February 2010 )