Quasi-Static Analysis of Flexible Pavements based on Resilient Modulus Master Curves of HMA

In order to consider the effect of loading time and temperature on the stiffness modulus of asphalt mixtures in current mechanistic-empirical pavement design methods, such as Mechanistic-Empirical Pavement Design Guide (MEPDG), the quasi-static analysis assuming elastic behavior of asphalt mixtures is employed instead of dynamic analysis assuming viscoelastic behavior of asphalt mixtures. In current procedures, quasi-static analysis of pavement is commonly accomplished by dynamic modulus. Nevertheless, previous studies have shown that the dynamic modulus is greater than the resilient modulus due to consideration of rest period for determination of resilient modulus of asphalt mixtures. Due to this reason, utilizing dynamic modulus for quasi-static analysis of pavements results in decreasing reliability of pavement design. This paper aims to propose a new method for quasi-static analysis of flexible pavements on the basis of resilient modulus master curves of asphalt mix under three loading waveforms of square, triangular and haversine. In the proposed method, the resilient modulus master curves under different loading waveforms are developed based on measured complex moduli and by employing linear viscoelastic theory. Comparison of fatigue life and rutting life resulting from the quasi-static analysis of pavement based on the dynamic modulus and resilient modulus shows that the pavement life is overestimated when the dynamic modulus master curve is used instead of resilient modulus master curves. Also, this paper shows that for more accurate quasi-static analysis of flexible pavements and to consider loading waveform as well as the rest period on the stiffness of asphalt materials, the dynamic modulus values should be used with the assumption of f = 1/2πt instead of f = 1/t.