Framework of Asphalt Balanced Mix Design (BMD) for New England Transportation Agencies

Asphalt mixture design in the New England region is performed based on the analysis of volumetric properties in the Strategic Highway Research Program’s Superpave mix design method. While the Superpave method has provided improvement over the design methods that preceded it, its limitations have emerged over the last two decades. One limitation is the apparent loss of mixture durability and increase in cracking potential due to the tendency of Superpave mixtures to have lower asphalt binder content than typically found with other methods. The increased use of recycled materials in asphalt mixtures has further exacerbated this problem as the aged asphalt within the recycled materials tends to stiffen and embrittle the mixes, making them more susceptible to durability problems. These issues with the Superpave method have led transportation agencies to seek out alternative mix design methods with an emphasis on performance testing in addition to, or as a replacement for, volumetrics. One of the more recently developed promising approaches is the balanced mix design (BMD). In principle, BMD is a design approach that provides asphalt mixtures that are resistant to rutting and cracking as indicated by performance testing. Because of the flexibility of balanced mix design, many transportation agencies across the country have expressed interest and, in some cases, have begun to require the BMD approach for mix approval. The development of a regional BMD approach needs to be tailored to the typical distress issues and materials in the region. While some New England states have expressed interest in the BMD approach, there have been no regional studies to investigate this approach for the region. The objective of this research project is to synthesize existing information and to develop recommendations for a rational BMD approach for use by the New England transportation agencies. Gaps in testing and performance data will be identified through this project and an experimental plan for required future work will be developed.