In order to properly characterize modified asphalt binders and mixes for Alaskan pavements, this study evaluated properties of 13 asphalt binders typically used in Alaska from three different suppliers, and 10 hot mix asphalt (HMA) mixtures which were either produced in the lab or collected from existing paving projects in Alaska. Various binder and mixture engineering properties were determined, including true high binder grades, complex modulus (G*), and phase angle ( ́) at high performance temperatures, multiple stress creep recovery rate and compliance, bending beam rheometer stiffness and m-value, Glover-Rowe parameter, T, rheological index, and crossover frequency for binders, and rut depth, critical strain energy release rate (Jc), Indirect tensile (IDT) creep stiffness and strength for mixtures. Binder cracking temperatures were determined using asphalt binder cracking device. Mixture cracking temperatures were determined with IDT creep compliance and strength data. It was found that rutting and cracking resistances of the mixtures with highly modified binders were better than the mixture with unmodified asphalt binder (PG 52-28). Future recommendations for highly modified asphalt binders applications and research were provided based on laboratory testing results and field survey evaluation.

The objective of the proposed research project is to determine the feasibility of utilization of laboratory blended ground tire rubber (GTR), terminally-blended GTR following Nevada Department of Transportation's (NDOT’s) specifications, or other crumb-rubber-modified (CRM) products to meet the rheological and engineering properties of asphalt modified binders and mixtures. The test results will be compared to styrene butadiene styrene (SBS) modified binders used in Nevada. The specific objectives of the research project will include the following: (1) Determining initial recommendations for terminally-blended GTR mix design guidelines based on the literature review and basic laboratory test results; (2) Investigating the rheological characteristics of various crumb rubber types (e. g. -30, -40, and terminal blend) at high, intermediate, and low performance temperatures through the performance of American Association of State Highway and Transportation Officials (AASHTO) standards and any other NDOT’s specification requirements; (3) Investigating the effects of various rubber modifiers on NDOT’s mix design including the mix volumetric properties such as air voids, voids in mineral aggregate (VMA), and optimum asphalt binder ratio specifications from AASHTO and NDOT; (4) Determining the Hveem stability, moisture susceptibility, permanent deformation, dynamic modulus, flow number characteristics of various alternate modifiers with hydrated lime in terms of specifications from AASHTO and NDOT; and (5) Developing recommended specifications for Nevada DOT regarding the utilization of these materials.