Evaluating Maryland Asphalt Mixtures Using Balanced Mix Design for Durable Pavements

While funding for highways is always uncertain, it is critical to look for ways to increase durability and make roads last longer. Balanced mix design is an approach that could help Maryland Department of Transportation State Highway Administration (MDOT SHA) improve durability. That National Center for Asphalt Technology defines balanced mix design as "asphalt mix design using performance tests on appropriately conditioned specimens that address multiple modes of distress taking into consideration mix aging, traffic, climate, and location within the pavement structure." The goal of this project is to design for performance, not just to the specification. To achieve that, MDOT SHA needs to establish base line criterion for cracking index and rutting tests for various Maryland mixes by using IDEAL Cracking Test (CT) and Indirect Tensile Strength (IDT) test methods. There is also a need to provide training on how to perform balanced mix design using the IDEAL CT and IDT tests and to write specifications for MDOT SHA's use. Moving from specification-driven, sometimes “dry” mixes to performance-tested mixes will help correct age durability issues. Optimum binder content needs to be closely evaluated. This research will accomplish the following: (1) establish a performance testing mix criteria; (2) provide guidance to characterize cracking and address it at the mix design stage; (3) develop potential surrogate test correlation for plants to use; and (4) develop a volumetric property baseline for mixtures.