Energy Based Laboratory Fatigue Failure Criteria for Asphalt Materials

The definition of fatigue failure in the laboratory is not only an important but also a controversial issue. Researchers have developed a number of fatigue failure criteria, including the most traditional one, which defines failure at the cycle to 50% initial modulus reduction. However, this definition is always challenged due to its lack of physical background. Recent studies showed that the dissipated energy ratio approach appears to be a favorable concept, which takes into account the fundamental dissipated energy evolution behavior of asphalt materials during a cyclic fatigue test. This paper conducted a review of three different energy based fatigue failure criteria and evaluated their applicability for fatigue data from asphalt binders and mixtures and under both stress and strain controlled loading modes. A macroscopic failure criterion is recommended, which is defined as the sudden change of the dissipated energy evolution curve and is consistently related to the beginning of macrocrack propagation. In addition, by comparing different failure criteria, the traditional 50 % initial modulus reduction criterion was found to have a strong correlation with energy based macroscopic fatigue failure for both mixtures and binders. It is thus suggested that the 50 % initial modulus reduction failure can be used as a simple but reasonable fatigue criterion, which indicates the transition from microcrack to macrocrack.