Developing an indicator for fatigue cracking in hot mix asphalt pavements using viscoelastic continuum damage principles

Fatigue cracking in asphalt pavements results in decreased ride quality, decreased fuel economy, and provides an avenue for intrusion of water. Design of the mixture is predominantly focused on volumetrically balancing the amount of air, asphalt, and aggregate in the system. Such an approach only implicitly considers performance and so the natural progression is to design through direct material property assessment and correlations to field performance. The objectives of this paper are to relate mixture stiffness, fatigue, and pavement system characteristics together for use in performance-based mixture design; identify a Simplified-Viscoelastic Continuum Damage model output parameter which produces the most separation between poorly and satisfactorily performing structures when combined with dynamic modulus and phase angle information; and evaluate the impact of reclaimed asphalt pavement on the performance of the indicator. Results show a relationship between fatigue life of the pavement system and an energy-based index. This approach holds promise because of its reliance on material attributes that can be derived on one testing machine. The constitutive model parameters can be found from the direct tension cyclic fatigue test and can be incorporated into prediction software, further enhancing the appeal of a performance specification.