Evaluation of Stiffness, Strength, and Ductility of Asphalt Binders at an Intermediate Temperature

The search for a test and parameter that can effectively describe the fatigue cracking resistance of an asphalt binder has led to many approaches. Of these, researchers have used stiffness, strength, and ductility-based criteria to screen binders on the basis of inherent resistance to cracking. In this study, poker chip testing on thin films of asphalt binder was used at intermediate temperatures to obtain both stress and ductility-based properties of eight binders. In addition, a dynamic shear rheometer frequency sweep at an intermediate temperature was conducted to obtain stiffnesses of the binders and a surrogate parameter for ductility. The results showed no relationship between strength and stiffness. In most cases, binders that were rated to have high ductility on the basis of the dynamic shear rheometer parameter also had high toughness on the basis of the poker chip test. However, some binders clearly departed from this trend, with at least one binder exhibiting both ideally desired high stiffness and toughness. Examination of failure surfaces from the poker chip test provided additional information about the mechanisms that drove failure.