BACKGROUND

Environmental sustainability and economic benefits motivate maximum use of recycled asphalt materials (RAM), including reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS), in asphalt mixtures. However, when stiff, brittle, aged materials are added to virgin asphalt-aggregate mixtures, adequate durability (initially and with time) must be maintained by engineering each unique combination of virgin and recycled materials. To maximize durability, state departments of transportation (DOTs) currently limit the RAP and RAS contents and their overall recycled binder ratio (RBR). Strategies for improving binder rheology and mixture durability include utilizing a softer base binder or adding a recycling agent (rejuvenator), but the durability of mixtures utilizing these strategies is unknown.

OBJECTIVES

The objectives of this research were: (1) produce a proposed AASHTO standard practice and associated test methods for design and evaluation of durable high RAM content asphalt mixtures and (2) revise the proposed AASHTO Standard Practice for Characterization of Asphalt Mixtures with High Recycled Materials Contents and Recycling Agents produced in NCHRP Project 09-58 to address mixture durability.

STATUS: Research completed. Publication decision pending.