Synthesis of Information Related to Highway Practices. Topic 52-17. Use of Recycling Agents in Asphalt Concrete Mixtures

The Federal Highway Administration (FHWA) has highlighted the importance of using recycled materials in the highway construction industry, due to the potential engineering, economic, and environmental benefits. The use of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) has increased in highway construction to reduce the amount of virgin and non-renewable materials. Mixtures containing RAP and RAS are significantly stiffer than virgin mixtures as RAP and RAS have experienced in-service aging. Although the use of RAP and RAS in new asphalt mixtures may increase the rutting resistance of pavements, it may also compromise cracking resistance. To avoid this problem, asphalt mixtures containing RAP and RAS usually require the use of a softer binder or recycling agents (RA). Not all departments of transportation (DOTs) have experience with mixtures containing RAP and RAS or with using recycling agents. Factors preventing the use of these materials include specification limitations, lack of expertise in processing RAP and RAS, lack of availability of quality RAP and RAS, processes and data to support the use of RA, and negative prior experiences. The objective of this synthesis is to document current DOT practices regarding the use of recycling agents in asphalt mixtures containing RAP and RAS. Information to be gathered includes (but is not limited to): DOT policies, specifications, definitions, and guidelines related to the use of RA (existing or under development); types and documented performance of RAs available for use in asphalt mixtures; factors limiting the use of mixtures containing RA; extent of use of RAP and RAS mixtures with RA and how long have they been used; methodology for determining type and dosage of RA including the specific products used; techniques for evaluating the performance of mixtures containing recycling agents (e.g., binder evaluation, mix performance tests, and long term aging); and procedures for acceptance and quality assurance (e.g., testing, inspection, traceability). Information will be collected through literature review, a survey of DOTs directed to the voting DOT members of the AASHTO Committee on Materials and Pavements, and follow-up interviews with selected agencies for the development of case examples. Information gaps and suggestions for research to address those gaps will be identified.


  • English


  • Status: Active
  • Funding: $45000
  • Contract Numbers:

    Project 20-05, Topic 52-17

  • 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:

    Gause, Jo

  • Performing Organizations:

    University of New Hampshire, Durham

    Department of Civil Engineering
    Durham, NH  United States  03824
  • Principal Investigators:

    Sias, Jo

  • Start Date: 20201006
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01739674
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 20-05, Topic 52-17
  • Files: TRB, RIP
  • Created Date: May 18 2020 3:05PM