Essential and Plastic Works of Ductile Fracture in Asphalt Binders and Mixtures

Fatigue evaluation of asphalt has historically been investigated with empirical tests that dynamically vary stresses or strains and consider the numbers of repetitions to failure. However, with such an approach it has been difficult to decide what constitutes a representative test for a particular application and hence, what constitutes a good binder. Stress controlled tests may rank binders differently from strain controlled tests. At present, there is no standard to unambiguously predict the fatigue life of asphalt. This paper explores the essential work of fracture method as based on a simple energy analysis during failure. The essential and plastic works of fracture for a large set of asphalt binders were determined and both were found to vary a great deal for binders of nearly the same Superpave grade. The mixture test results show that the essential works of fracture for binder and mixture are reasonably correlated but that the former is approximately ten times tougher than the latter. Plastic works of fracture in the binder show less correlation with those in the mixture. It is believed that the asphalt binder test method, as developed, shows promise for fatigue fracture performance ranking.