Considering Binder Availability of Recycled Asphalt Materials

To promote sustainability and ensure adequate performance, there is a need to consider the amount of asphalt binder available from asphalt-based recycled materials, such as reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS). The use of recycled materials is growing due to economic and environmental benefits, yet there is no accepted method to quantify or account for the effective binder content available from these materials. AASHTO guidance on the design of asphalt mixtures with RAP and/or RAS assumes that 100% of the recycled binder is available to blend with virgin binder and any additives such as recycling agents or warm mix asphalt products. The actual availability of recycled binder varies between 0% and near 100%, with lower availability for heavily aged RAP or RAS binder and mixtures produced at lower temperatures. Thus, the assumption of 100% availability leads to less overall effective binder content, yielding a dry mixture with insufficient coating that may be difficult to compact and that may exhibit inadequate durability and cracking performance in-service. These poor-performing pavements cost agencies due to their reduced life and increased maintenance expenditures. This research will identify or develop a method to quantify or account for binder availability from recycled asphalt materials and provide guidelines for their efficient use. The objective of this research is to identify or develop a method to quantify or account for binder availability from recycled asphalt materials that can be used by agencies to improve mix design procedures and specifications. Important factors affecting the active binder inherent in recycled materials and/or the available binder that contributes to the recycled mixture include the following to be considered when producing guidelines for efficient use of RAP/RAS: (a) the type and source (aging state), content (%), binder content, and gradation of the recycled material; (b) the performance grade and flexibility of the virgin binder; (c) the gradation of the virgin aggregate; (d) the type and dose of optional additive(s) including recycling agents or warm mix asphalt additives; and (e) production plant type and mixing and storage times and temperatures. Accomplishment of this objective shall require the following tasks: (1) review current practices of U.S. and international agencies to estimate and incorporate recycled binder availability; (2) evaluate coatability and rutting and cracking performance of typical dense-graded mixtures considering 100% recycled binder availability and 0% recycled binder availability to assess the impact on mixture performance; (3) identify or develop a method to quantify or account for recycled binder availability that is sensitive to the factors listed above; and (4) develop a reporting format for characterizing RAP/RAS in terms of binder availability. Project deliverables shall include the following: (1) a user-friendly method to incorporate binder availability factors for RAP and RAS into mix design processes and (2) proposed revisions to specifications and mix design procedures for recycled mixtures to account for recycled binder availability.


  • English


  • Status: Proposed
  • Funding: $500000
  • Contract Numbers:

    Project 09-68

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Harrigan, Edward

  • Start Date: 20210525
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01772927
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 09-68
  • Files: TRB, RIP
  • Created Date: May 24 2021 3:14PM