Statewide Assessment of Balanced Mixture Design for New York State's Asphalt Mixtures

As state agencies want greater assurance that their asphalt materials will last longer, the inclusion of performance testing during mixture design and production has gained popularity. In particular, the concept of determining the asphalt content that optimizes asphalt mixture rutting and fatigue cracking resistance, called balanced mixture design (BMD), is being explored in the U.S. In this study, the New York State Department of Transportation (NYSDOT) orchestrated a statewide evaluation of their asphalt mixtures under the BMD concept. Eleven asphalt mixtures, representing a majority of what is utilized as surface courses on New York (NY) asphalt pavements, were first volumetrically verified and then evaluated using BMD to determine the range of asphalt content where rutting and fatigue cracking resistance optimization are achieved. Three laboratory rutting tests (asphalt pavement analyzer [APA], Hamburg wheel tracking [HWT], and high temperature indirect tensile strength [HT-IDT]), and three fatigue cracking tests (overlay tester, semi-circular bending [SCB] flexibility index, and indirect tensile asphalt cracking test [IDEAL-CT] index) were utilized during the performance testing. The results showed that 6 of the 11 volumetrically designed asphalt mixtures were under-asphalted with respect to achieving minimum fatigue cracking resistance based on the laboratory tests. None of the volumetrically designed asphalt mixtures were determined to have rutting issues. The addition of polymer modification in the asphalt binders was found to increase the range of asphalt contents achieving a balanced condition. The study also showed that, when appropriate performance criteria are selected, it is possible to utilize different test methods.