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.
• Cavalli, M. C., Partl, N., and Poulikakos, L. D. (2019). “Effect of Ageing on the Microstructure of Reclaimed Asphalt Binder with Bio-based Rejuvenators.” Road Materials and Pavement Design, 1-12.
• Epps Martin, A., Kaseer, F., Arámbula-Mercado, E., Bajaj, A., Garcia Cucalon, L., Yin, F., Chowdhury, A., Epps, J., Glover, C., Hajj, E.Y., Morian, N., Sias Daniel, J., Oshone, M., Rahbar-Rastegar, R., Ogbo, C., and King, G. (2019). Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios. Pre-publication draft of NCHRP Research Report 927. Transportation Research Board, Washington, D.C.
• Tang, S., Williams, R. C., and Cascione, A. (2017). “Reconsideration of the Fatigue Tests for Asphalt Mixtures and Binders Containing High Percentage RAP.” Pavement Eng. 18(5), 443-449.
• Zaumanis, R., Mallick, R., and Frank, R. (2014). Evaluation of Rejuvenator’s Effectiveness with Conventional Mix Testing for 100% Reclaimed Asphalt Pavement Mixtures. Transportation Research Record: Journal of the Transportation Research Board, 2370, 17–25.
Jo Allen Gause
First Panel: October 6, 2020, Washington, DC
Teleconference with Consultant: October 30, 2020 from 10:30 a.m., Eastern
Second Panel: June 22, 2021, Washington, DC
Judith Corley-Lay, National Center for Pavement Preservation
Stacey Diefender, Virginia Department of Transportation
Adam Hand, University of Nevada
Thomas Kane, New York Department of Transportation
Jacob Lautanen, Ohio Department of Transportation
Robert Rea, Nebraska Department of Transportation
Jesus Sandoval-Gil, Arizona Department of Transportation
David Mensing, Federal Highway Administration
Nelson Gibson, Transportation Research Board