Fatigue Characterization of HMAC Mixtures Using Mechanistic Empirical and Calibrated Mechanistic Approaches Including the Effects of Aging

Laboratory fatigue characterization of HMAC mixtures constitutes a fundamental component of pavement design and analysis to ensure adequate performance. In this study, the traditional mechanistic empirical (ME) approach and a continuum micromechanics based calibrated mechanistic approach with surface energy (CMSE) measurements were comparatively utilized to characterize the fatigue resistance of two HMAC mixtures in the laboratory, including investigating the effects of aging. Although the results were comparable, the CMSE approach exhibited greater flexibility and potential to discretely account for most of the fundamental material properties (including fracture, aging, healing, visco-elasticity, anisotropy, crack initiation, and crack propagation) that affect HMAC pavement fatigue performance. Compared to the mechanistic-empirically based ME approach, the CMSE approach is based on the fundamental concepts of continuum micromechanics and energy theory; and utilizes the visco-elastic correspondence principle, Paris' Law of fracture mechanics, and Schapery's work potential theory to monitor cumulative fracture damage in HMAC mixtures, measured in terms of dissipated pseudo strain energy (DPSE) under repeated uniaxial tensile tests. Additionally, the CMSE results exhibited relatively lower statistical variability. For the materials and test conditions considered in the study, aging reduced HMAC mixture fatigue resistance and its ability to heal. Thus aging plays a significant role in HMAC mixture fatigue performance and should be incorporated in fatigue design and analysis.