Component Materials Selection Guidelines and Evaluation Tools for Binder Blends and Mixtures with High Recycled Materials Content and Recycling Agents

摘要

Increasing the quantity of recycled materials in asphalt mixtures provides economic and environmental benefits, but engineering concerns remain, including construction issues with workability and compaction and inadequate performance in terms of cracking resistance due to the addition of stiff, brittle, aged reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS). These drawbacks can be overcome by the use of more ductile base (virgin) binders and/or the use of recycling agents (also known as rejuvenators). The effectiveness of the recycling agent in binder blends and mixtures with high recycled materials content and its evolution with aging depends on a number of factors including the source and grade of the base binder; the type, source, and amount of recycled materials; and the type and dose of the recycling agent. A wide variety of component materials and their combinations were utilized in a multi-year research project that included laboratory testing and field performance monitoring of test sections in five states. Component materials included nine base binders, six RAP sources, five RAS sources including manufactured waste and tear-offs, and ten recycling agents that spanned five different types. Different materials combinations were used throughout this study to examine the interaction of the factors by binder/binder blend and mixture testing and analysis. This paper summarizes the primary product from this extensive study—a draft AASHTO standard practice for the use of recycling agents in asphalt mixtures with high recycled materials content that includes: (1) component materials selection guidelines for base binders, recycled materials, and recycling agents; (2) a recycling agent dose selection method; (3) materials proportioning guidance; (4) binder blend rheological evaluation tools; and (5) mixture performance evaluation tools. Example results that support the proposed guidelines, tools, and thresholds are also provided.