1371946 - Development of a New Balanced Mix Design (BMD) Framework that Incorporates Binder Tests

The study focuses on the development of a new Balanced Mix Design (BMD) framework that incorporates binder tests. With the surge in the use of modified asphalt binders throughout the world, it is important to examine the binders for performance outside of their linear viscoelastic (LVE) range. Modified asphalt binders, usually costlier, are expected to increase the service life of asphalt pavements. The study first utilizes two approaches to evaluate the nonlinear viscoelastic and failure performance of eight novel modified asphalt binders. First, the poker chip test for cracking performance evaluation was conducted at different loading rates and aging levels. The results conclude the efficacy of the poker chip test to differentiate and rank the best-performing modified asphalt binders. Furthermore, the impact of varying the loading rates, aging levels, modifications, and performance grades was also studied. These results indicated that loading rates ranging from 1 to 4 N/sec can be used to differentiate modified binder performance, which allows a wider range of machines to be used to do this test. In addition, the impacts of aging were studied to introduce differentiation between modifiers that are sensitive to aging. Apart from this, the Multiple Stress and Creep Recovery (MSCR) test were conducted to evaluate the rutting performance. MSCR results further augmented the confidence in initial rankings as polymer-modified binders showed superior performance to other modifier types. It was observed that the top two binders in terms of poker chip results also had the best MSCR performance. Hence, instead of balancing the performance, like is done for mixtures, between rutting and cracking performance, an optimum binder can be synthesized which has excellent performance against load-related cracking and permanent deformation. This sets the stage for a balanced binder synthesis process to be implemented into future specifications and research efforts. As a part of ongoing research, the asphalt mixture specimens were tested for cracking and rutting performance using the Illinois Flexibility Index Test (I-FIT) and Hamburg Wheel-Tracking Device, respectively. The results were used to propose the thresholds for the poker chip test. Furthermore, a new Balanced Mix Design (BMD) approach is also proposed, which includes testing asphalt mixtures for cracking and rutting performance using the Illinois Flexibility Index Test (I-FIT) and Hamburg Wheel-Tracking Device, and asphalt binders for cracking and rutting performance using the Poker Chip Test and Multiple Stress and Creep Recovery (MSCR), respectively.