Mixing and Compaction Recommendations for Warm Mix Asphalt (WMA) with Recycled Asphalt Shingles (RAS)

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CAIT project no.: CAIT-UTC-028

Fiscal Year: 2012/2013

Status: Final

Rutgers-CAIT Author(s): Thomas Bennert, Ph.D., Patrick Szary, Ph.D.

External Author(s): Eileen Sheehy, NJDOT Project Manager

Sponsor(s): New Jersey Department of Transportation, FHWA-NJ


The use of recycled asphalt shingles (RAS) is an attractive option for asphalt mixture producers due to the high amount of recycled asphalt binder available in RAS. By weight, RAS contains 10 to 25 percent asphalt by total weight of the shingle.

The asphalt binder in RAS is generally much stiffer than conventional paving asphalts due to the requirements of the roofing shingle industry. This increase in asphalt binder stiffness generally results in a stiffer asphalt mixture that is more difficult to compact in the field. Some asphalt mixture suppliers are looking at using warm mix asphalt (WMA) technologies to help with compaction, but there is limited information on the use of WMA with RAS and how the mixing and compaction properties are influenced.

With the transportation infrastructure industry moving toward sustainable technologies and recycling when possible, the use of recycled asphalt shingles (RAS) in hot mix asphalt looks appealing. However, the handling and performance of these mixtures is still highly questioned and viewed as potentially problematic by most agencies.

Rutgers conducted a laboratory study to evaluate the impact on recycled asphalt shingles (RAS) on the compactability of asphalt mixtures. Two different methodologies were used in the study: 1) Asphalt binder-based testing; and 2) Asphalt mixture-based testing.

In addition to the RAS, two different types of WMA technologies were included to evaluate the change in asphalt compactibility. The results of the study showed that performance grading of the RAS required:

  • the RAS to be blended with a much softer asphalt binder at varying percentages;
  • the inclusion of recycled asphalt shingles, whether they are post manufacturer or post consumer, will detrimentally impact the mixing and compaction properties of the asphalt mixtures; and
  • that the addition of WMA technologies to the RAS asphalt mixtures does appear to aid in the compaction properties of the final asphalt mixture.