Evaluation of Fatigue Models of Hot-Mix Asphalt Through Laboratory Testing

Many studies have investigated the fatigue resistance of hot-mix asphalt (HMA) mixtures on the basis of the material properties and structural responses. In this study, a four-point bending-beam fatigue apparatus was used to measure the fatigue life of a typical Michigan HMA mixture under various frequencies (1, 5, and 10 Hz) and temperatures (4 degrees C, 13 degrees C, and 21.3 degrees C). The objective of this study was to evaluate laboratory models for predicting fatigue over wide ranges of testing conditions to rank their fatigue performance on the HMA mixtures. In addition, this paper aimed to correlate the flexural stiffness (modulus) with dynamic modulus, because the dynamic moduli of HMA are key input parameters in the Mechanistic-Empirical Pavement Design Guide (MEPDG). The correlation results showed a strong linear correlation between the flexural stiffness and dynamic modulus, with the flexural stiffness being 30% lower than the dynamic modulus. By providing a linkage between dynamic modulus and flexural stiffness, the study helped to substantiate the concept of using dynamic modulus in the MEPDG or to evaluate rutting. In addition, Rowe and Bouldin's stiffness degradation concept was used to compare the ability of different models to predict fatigue life. The results of this study showed that the energy-based fatigue prediction model, which considered rest periods, various testing temperatures, and loading frequencies, correlated well with the laboratory-determined fatigue life.