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.

The purpose of this study is to evaluate warm mix asphalts (WMA) with recycled asphalt pavement (RAP) from Nevada. For this study, four different warm mix technologies and four different aggregate sources with two different percentages of recycled asphalt binder ratios were used. Aggregates from Lone Mountain, North Tenaya, Spanish Springs and Lockwood were used with appropriate binders for the particular climate conditions in those areas. All the aggregates were lime-marinated, as per requirement of the Nevada Department of Transportation. Advera, Evotherm 3G, Sonnewax and waterfoam were the warm mix technologies evaluated. All four WMA mixtures satisfied all the criteria for resistance to moisture damage with or without RAP for all the aggregate sources used. In terms of fatigue, the WMA mixtures showed better results than the HMA mixture. But for the rutting resistance all of the WMA mixtures showed lower values than the HMA mixtures. This was expected, even though the WMA's rutting resistance improved when RAP was added.

The state of Nevada is experiencing permanent deformation problems with hot mix asphalt pavements at or near intersections. The Nevada Department of Transportation (NDOT) is currently using a Type 2C dense graded mixture in most of its construction. The NDOT Type 2C mixture showed excellent rutting resistance under normal highway traffic, while its resistance to rutting and shoving at intersections in the hot environment of Las Vegas is questionable.The overall objective of this research was to identify a hot mix asphalt (HMA) mixture with good resistance to rutting and shoving at intersections. To this end, two laboratory evaluations were conducted: I. Postmortem evaluation of in-service intersections and II. Laboratory evaluation of different aggregate gradations. Based on past performance and data generated from this research, five different aggregate gradations were selected for laboratory evaluation. Aggregates were sampled from the Sloan quarry located south of Las Vegas, Nevada, along Interstate 15. All five gradations were mixed with a polymer-modified PG76-22NV asphalt binder which is the current specified asphalt grade for southern Nevada. A Hveem mix design was conducted for each of the five mixtures. This part of the research re-evaluated the APA and RSCH as potential candidates for a mix design test for intersection mixtures. In addition, the triaxial compression strength test and the repeated load triaxial test (RLT) were also evaluated. All tests ranked the permanent deformation resistance of the five mixtures in the same order. Additionally, dynamic mechanistic analyses were performed as an attempt to determine the pavement responses under a heavy loaded truck at and away from the intersection. The findings of the mechanistic analyses were used to predict permanent deformation potential in the HMA layer. To this end, permanent deformation models for NDOT Type 2C mixture were developed in the laboratory using the repeated load triaxial (RLT) and the repeated shear at constant height (RSCH) testing. The actual specifications used by NDOT for the various permanent deformation tests were reviewed and adjusted for the HMA mixtures that are going to be used at intersections and stopping areas. (Abstract shortened by UMI.)

The intention of this research effort is to evaluate the use of warm mix additives with typical polymer-modified and terminal blend tire rubber asphalt mixtures from Nevada and California. The research effort is broken into three phases that are intended to evaluate the impacts of warm mix additives with typical polymer-modified and terminal blend tire rubber asphalt mixtures from Nevada and California: moisture damage, performance characteristics, and mechanistic analysis. In Phase I of this research effort, mixture resistance to moisture damage was evaluated using the indirect tensile test and the dynamic modulus at multiple freeze-thaw cycles. Laboratory testing was conducted to address the following: (1) the impact of warm mix additive and reduced production temperatures on the moisture damage resistance of asphalt mixtures, (2) the impact of residual aggregate moisture on the moisture damage resistance of WMA mixtures, (3) the impact of warm mix additives on the moisture damage resistance of anti-strip treated WMA mixtures, and (3) the impact of long-term aging on strength gain and the moisture damage resistance of WMA mixtures. A total of one aggregate source, four warm mix asphalt technologies (Advera, Sasobit, Revix and Foaming) and three asphalt binder types (neat, polymer-modified and terminal blend tire rubber modified asphalt binders) typically used in both Nevada and California are being evaluated in this study. This thesis will only summarize the test results and findings of the Phase I of the study for two warm-mix additives: Advera and Sasobit. The evaluation of the other two technologies (i.e. Revix and Foaming) as well as the Phase II testing are still in progress and have not been completed.

TRB's National Cooperative Highway Research Program (NCHRP) Report 752: Improved Mix Design, Evaluation, and Materials Management Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content describes proposed revisions to the American Association of State Highway and Transportation Officials (AASHTO) R 35, Superpave Volumetric Design for Hot Mix Asphalt, and AASHTO M 323, Superpave Volumetric Mix Design, to accommodate the design of asphalt mixtures with high reclaimed asphalt pavement contents.