Final Scope

Reclaimed asphalt pavement (RAP) has been used in pavement rehabilitation and construction for decades. Due to the potential engineering, economic, and environmental benefits, FHWA has highlighted the importance of using RAP in the highway construction industry. In recent years, several state DOTs have introduced special provisions and specifications to allow the use of high RAP contents in asphalt mixtures. NCHRP Project 09-58 defines high RAP mixtures as those characterized by high recycled binder ratios (RBRs), typically greater than 0.3. Nevertheless, the definition of “high RAP mixtures” remains state-specific. Some state DOTs have had effective practices, while some state DOTs have had challenges specifying, designing, and controlling the quality of asphalt mixtures containing RAP, especially those with high contents. Not all state DOTs have experience with mixtures containing higher RAP contents than those allowable according to their current specifications. Therefore, there is a need for a comprehensive study on current state DOT practices to capture the benefits, challenges, and responsible implementation of high RAP mixtures.

The objective of this synthesis is to document current state DOT practices regarding the design, production, and placement of high RAP content mixtures.

Information to be gathered includes (but is not limited to):

• DOT definitions, policies, specifications, and guidelines related to designing, producing, and placing high RAP mixtures (existing and/or under development);
• What strategies are state DOTs using for high RAP, including but not limited to balanced mix design (BMD), binder availability (reclaimed binder ratio), recycling agents, soft binders, etc.;
• Quality assurance program for RAP or the quality assurance of the overall mix including but not limited to DOT policies, specifications, and guidelines related to RAP stockpile management and testing;
• What are the barriers or challenges that state DOTs face when using high RAP;
• State DOT field experiences (e.g., production and placement) with high RAP mixtures, as well as long-term field performance.

Information will be gathered through a comprehensive literature review, a survey of state DOTs, and follow-up interviews with selected DOTs with relevant experience to develop case examples. Information gaps and suggestions for research to address those gaps will be identified and presented.

Information Sources (Partial)

• Diefenderfer, S. D., Habbouche, J., and Boz, I. (2023). “Balanced Mix Design for Surface Asphalt Mixtures: 2020 Field Trials.” VTRC 23-R13. Virginia Transportation Research Council, Charlottesville, VA.
• Sias, J. E., Dave, E. V., and Zhang, R. (2022). NCHRP Synthesis 586: Use of Recycling Agents in Asphalt Concrete Mixtures. Transportation Research Board, Washington, DC.
• Hand, A. J. T., and Aschenbrener, T. B. (2021). “Successful Use of Reclaimed Asphalt Pavement in Asphalt Mixtures.” WRSC-TR-21-10. University of Nevada, Reno.
• FHWA (2021). “Resource Responsible Use of Reclaimed Asphalt Pavement in Asphalt Mixtures.” FHWA-HIF-22-003. Washington, DC.
• Diefenderfer, S. D., Boz, I., and Habbouche, J. (2021). “Balanced Mix Design for Surface Asphalt Mixtures: 2019 Field Trials.” VTRC 21-R21. Virginia Transportation Research Council, Charlottesville, VA.
• Habbouche, J., Boz, I., Underwood, B. S., Castorena, C., Gulzar, S., Fried, A., and Preciado, J. (2021). “Review From Multiple Perspectives for the State of the Practice on the Use of Recycled Asphalt Materials and Recycling Agents in Asphalt Concrete Surface Mixtures.” Transportation Research Record 2676, pp. 407-420. Transportation Research Board, Washington, DC.
• Epps-Martin, A., Kaseer, F., Arámbula-Mercado, E., Bajaj, A., Cucalon, L.G., Yin, F., Chowdhury, A., Epps, J., Glover, C., Hajj, E.Y., Morian, N., Daniel, J.S., Oshone, M., Rahbar-Rastegar, R., Ogbo, C., and King G. (2020). NCHRP Research Report 927: Evaluating the Effects of Recycling Agents on Asphalt Mixtures With High RAS and RAP Binder Ratios. Transportation Research Board, Washington, DC
• Federal Highway Administration (2018). State of the Knowledge for the Use of Asphalt Mixtures with Reclaimed Binder Content. FHWA-HIF-18-059. Washington, DC.
• Stroup-Gardiner, M. (2016). NCHRP Synthesis 495: Use of Reclaimed Asphalt Pavement and Recycled Asphalt Shingles in Asphalt Mixtures. Transportation Research Board, Washington, DC.

TRB Staff
Zhiye Li
Email: zli@nas.edu

Meeting Dates
First Panel Meeting Date: 03/06/2025 (In-person, in Washington, DC)
Teleconference with Consultant: 04/17/2025 (Virtual, via Zoom) 
Second Panel Meeting Date: 12/10/25 (In-person, in Washington, DC)