Evaluation of Nevada's hot mix asphalt mixtures using tire rubber modified binders

The Nevada Department of Transportation (NDOT) currently uses two binder grades the PG64-28NV and the PG76-22NV in the northern and the southern parts of the state, respectively.; This research effort evaluated the laboratory performance of the hot mix asphalt (HMA) mixtures made with polymer modified binders the PG64-28NV and the PG76-22NV and the performance of the HMA mixtures made with rubber modified and the PG64-28TR and the PG76-22TR. The four mixtures were evaluated in terms of rutting resistance, fatigue cracking resistance, thermal cracking resistance, dynamic modulus, and moisture sensitivity. Two aggregate gradations were used for the northern (Lockwood) and the southern (Sloan) parts of Nevada. The PG64-28NV and the PG64-28TR binders were mixed with Lockwood aggregates, and the PG76-22NV and the PG76-22TR were mixed with Sloan aggregates.; Laboratory experiments were conducted at the Western Regional Superpave Center (WRSC) at the University of Nevada Reno (UNR). The flexural beam fatigue test was conducted to evaluate the resistance of the various mixtures to fatigue cracking. The repeated load triaxial and the asphalt pavement analyzer tests were used to evaluate the resistance of the various mixtures to rutting. The resilient modulus test was conducted to evaluate the resistance of the various mixtures to moisture sensitivity. The thermal stress restrained specimen test was conducted to evaluate the fracture temperatures of the PG64-28NV mix and the PG64-28TR mix. Additionally the dynamic modulus test was used to evaluate the stiffness of the various mixtures at various temperatures and time of loading.; Additionally, mechanistic analyses have performed to determine the pavement responses for each mixture. Four pavement structures, representing the four mixtures of asphalt with the same base and subgrade were analyzed under an axle load of 18 kips. This load is the maximum allowable axle load by NDOT. The responses in the HMA layer were calculated using the ELSYM5 software and the results were plugged into the laboratory developed performance models to evaluate the number of load repetitions to failure. The time and temperature dependent behavior of the HMA layer under a slow and high moving truck at low and high speeds (2 and 45 mph) is incorporated using the dynamic modulus of each mixture at the corresponding speed and temperature. The base course and subgrade layers were treated as linear elastic materials.