Development of a fatigue index parameter, <i> S <sub>app</sub> </i> , for asphalt mixes using viscoelastic continuum damage theory
Yizhuang David Wang, B. Shane Underwood, Y. Richard Kim
Abstract
Fatigue cracking is one of the major distresses in asphalt pavements. Engineers have used many methods, from sophisticated numerical simulations to experience-based knowledge, to address fatigue cracking and deliver pavements that perform well. One strategy that has become increasingly widespread is the use of a fatigue index parameter that identifies the cracking potential of asphalt mixtures independent of the pavement structure. The use of such indices allows pavement engineers to make quick and targeted decisions with regard to mix design, mix acceptance, and mix quality assurance. This paper proposes a new fatigue index parameter, Sapp, which represents the damage capacity of a mixture and is based on the viscoelastic continuum damage theory. Unlike other indices, this new index considers the effects of both material toughness and stiffness. Sapp was employed in this study to evaluate 105 different asphalt mixtures with varied design factors. The results indicate that Sapp is able to distinguish the fatigue resistance of asphalt mixtures with varied properties, including different binder contents, binder performance grades, reclaimed asphalt pavement contents, types of binder modifier, air void contents, aggregate gradations, and aging levels. This paper also presents a set of recommended Sapp threshold values for different expected traffic volumes.