Energy-Based Approach to Predict Thermal Fatigue Life of Asphalt Mixes Using Modified Uniaxial Test Setup

In this paper an energy-based approach has been proposed based on the principals of nonlinear viscoelastic fracture mechanics to determine the thermal fatigue life of asphalt mixes for the short-term aging condition at a constant temperature. The approach, presented in this paper for only one aging condition at one temperature, is considered in another paper as the basis for the development of a comprehensive model (TFCMODEL) by which the thermal fatigue life of various asphalt mixes may be predicted analytically for varying aging conditions and temperatures. To this end, a modified uniaxial test setup was designed to account for the effects of the bonding/friction condition between asphalt and base layers, and nonuniform distribution of stresses/strains within the asphalt layer depth. To characterize the thermal fatigue behavior of asphalt mixes, uniaxial thermal fatigue tests were carried out on the beam specimens at two aggregate gradations, two binder contents, two air void contents, one aging condition, one temperature, two bonding/friction conditions between the asphalt and base layers, and four cyclic loading patterns in both tension and compression, with three replicates. After determining the crack growth rate for the successive cycles, some empirical models were formed to predict the crack length and the maximum measured tensile/compressive loads as functions of the cycle number. Rate of dissipated pseudostrain energy, pseudo $J$-Integral, and the fracture parameters ($A$ and $n$) were then calculated for all the experimental combinations, and two empirical models were developed to predict the fracture parameters based on the viscoelastic properties of asphalt mixes. Finally, the thermal fatigue lives of asphalt mixes were obtained based on the change in the ratio of cumulative dissipated pseudostrain energy as the criterion identifying the thermal fatigue crack initiation and propagation.