| Load associated fatigue cracking is one of the major distress types occurring in flexible pavement systems. Asphalt Concrete (AC) mixtures flexural beam fatigue testing in the laboratory has been used for several decades and is expected to be an integral part of the new Superpave advanced characterization procedure. However, there is a great need to assess and develop a fatigue criterion based on initial and failure stiffness of the mixture under consideration. There is also a lack of fatigue database/models of typical AC mixtures that are utilized by transportation agencies for their implementation of the 2002 Design Guide. A major objective of this study was to develop revised AC fatigue models for the Arizona Department of Transportation (ADOT) for their future use in the 2002 Design Guide.; A laboratory testing program was performed on typical dense-graded and asphalt rubber gap-graded ADOT mixtures. Stress and strain controlled fatigue tests were conducted according to American Association of State Highway and Transportation Officials (AASHTO) procedures on six mixtures at three temperatures. At least 48 specimens for each mix were tested to establish representative fatigue curves. Test results indicated that the fatigue failure stiffness should be taken at 50 percent of the initial stiffness except for the cumulative dissipated energy, which should be taken at 30 percent of the initial stiffness. A stiffness degradation model was developed and presented in verification of the failure definition recommended by AASHTO. This model provides predictions of the damage relationship throughout the life of the mix during the fatigue test.; Surrogate fatigue models that accurately represent the fatigue behavior of Arizona AC mixes were developed. The primary advantage of these models is that extensive fatigue testing can be eliminated in the mix design process, as laboratory testing is only required to determine mix stiffness and phase angle.; Finally, a unique fatigue relationship was developed that relates fatigue life to the cumulative dissipated energy, which is independent on the mode of loading, temperature, frequency, or mix formulation. This method has the potential for unifying current fatigue analyses using a rational energy-based approach. |
