Capturing Durability of High Recycled Binder Ratio (RBR) Asphalt Mixture

Environmental sustainability and economic benefits motivate maximum use of recycled asphalt materials, including reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS), in asphalt mixtures. However, adequate cracking performance initially and with time when these stiff, brittle, aged materials are added to virgin asphalt-aggregate mixtures must be maintained by engineering each unique materials combination of virgin and recycled materials. To preclude cracking, state departments of transportation (DOTs) currently limit the RAP and RAS contents and their overall recycled binder ratio (RBR). Strategies for partially restoring rheology and improving cracking performance include utilizing a softer base binder or adding a recycling agent (rejuvenator), but the durability of these strategies with aging and exposure to moisture is unknown. In addition, these types of high RBR asphalt mixtures must be included in balanced mix design systems currently being implemented. A comprehensive standard practice and/or system is needed to specifically address the complexity of engineering durable, high RBR asphalt mixtures with balanced performance to promote environmental sustainability of the most recycled product in the United States and realize significant economic benefits. The objective of this research is to expand and update the draft AASHTO Standard Practice produced in NCHRP Project 09-58 for high RBR asphalt mixtures to address durability with tools to evaluate moisture susceptibility, updated aging protocols, and verified cracking performance thresholds. Accomplishment of this objective shall require the following tasks: (1) evaluate tests and methods for characterizing moisture susceptibility of asphalt mixtures, including the guidelines developed for warm-mix asphalt (WMA) in NCHRP Projects 09-49 and 09-49B; (2) review aging protocols developed in past NCHRP studies; (3) define practical parameters to capture field aging of high RBR mixtures in the laboratory that include initial quality and rate of aging; (4) further verify cracking performance thresholds developed in NCHRP Project 09-58 and evaluate alternate cracking tests and thresholds recommended in NCHRP Projects 09-57 and 09-57A; and (5) expand and update the draft AASHTO Standard Practice for high RBR asphalt mixtures produced in NCHRP Project 09-58 to include durability in terms of moisture susceptibility and aging.

Language

  • English

Project

  • Status: Proposed
  • Funding: $750000
  • Contract Numbers:

    Project 09-65

  • 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: 20200520
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01739634
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 09-65
  • Files: TRB, RiP
  • Created Date: May 18 2020 3:06PM