Synthesis for Quantification of Binder Availability in Recycled Materials [Project Title from Cover]

US Transportation Collection2021PDFTech ReportMartin, Amy EppsArambula-Mercado, EdithAbdelaziz, AmalTexas A&M Transportation InstituteTexas. Dept. of Transportation. Research and Technology Implementation OfficeUnited States. Department of Transportation. Federal Highway AdministrationTexas A&M Transportation InstituteUnited StatesTexasBinder contentMix designRecycled materialsSuperpaveReclaimed asphalt pavementsHot mix asphaltLiterature reviewsRecycled binder availabilityHigh recycled binder ratio (RBR)Recycled asphalt mixturesFHWA/TX-21/0-7062-R1BProject 0-7062October 2019\u2013October 2020Increasing recycled material content in asphalt mixtures provides economic and environmental benefits, but each unique material combination of virgin and recycled materials and additives must be engineered to ensure adequate performance with proper selection of component materials and balanced proportioning, as well as consideration of recycled binder availability. The design of mixtures with recycled materials often assumes that 100 percent of the recycled binder is available to blend with the virgin binder, and the virgin binder content is reduced accordingly. In reality, when recycled binder availability is less than 100 percent for heavily aged materials, total binder contents are less than optimum from mix design, resulting in dry mixtures with insufficient coating and inadequate durability and cracking performance. In addition, recycled binder availability can be used to assess aging state and preclude the use of large quantities of these materials with stiff, brittle binders that contribute negatively to performance even if available. This synthesis project addressed these issues by reviewing the literature available on the topic of recycled binder availability, collecting information on the state of the practice regarding recycled binder availability, performing a detailed analysis on three different recycled binder availability quantification methods, and revising the Texas Department of Transportation balanced mix design spreadsheet for Superpave mixtures to incorporate recycled binder availability.125