Construction of triaxial dynamic modulus master curve for asphalt mixtures

The dynamic modulus is considered as the most important factor of asphalt concrete influencing the field performance of asphalt pavements. The newly developed Mechanistic-Empirical Pavement Design Guide (MEPDG) used the uniaxial dynamic modulus master curve to characterize the temperature and time dependent behavior of asphalt concrete. It is evident that the triaxial dynamic modulus can better characterize the in situ mechanical behavior of the material. This study proposed a model for the construction of triaxial dynamic modulus master curve. A key feature of the proposed model is that it employs the vertical shifting technique to take into account the effect of confining pressure on the dynamic modulus. The vertical shift factor is modeled as a function of the reduced frequency and confining pressure. The triaxial master curve model was evaluated using dynamic modulus test results of three asphalt mixtures obtained at various temperatures, loading frequencies and confining pressures. The predictive accuracy of the proposed model is about the same as that of uniaxial and isobaric master curves, indicating the proposed model is accurate and effective in constructing triaxial dynamic modulus master curves.