Selection of Binder Performance Indicators for Asphalt Rutting Based on Triaxial and Wheel Tracking Tests

摘要

There is a need for true performance indicators for bituminous binders, which are equally applicable independent of whether the binder is modified or not. The purpose of this research is to evaluate performance indicators for permanent deformation both for modified and unmodified binders, and to select those indicators that relate best to permanent deformation in laboratory asphalt mix tests. The binder indicators considered are mainly rheological parameters, including the SHRP rutting parameter, the zero shear viscosity and the recently proposed repeated creep test. To evaluate the permanent deformation or rutting susceptibility of the corresponding mixes two devices were used: the French rut tester (large size device, according to EN 12697-22) and the cyclic triaxial compression test, according to EN 12697-25, part B. This study shows that rheological and even conventional properties of modified binders can be extremely dependent on the thermal history and preparation conditions prior to testing. A very strict control of these parameters is absolutely necessary in order to be able to determine repeaTable and reproducible binder performance indicators. The thermal history effects are related to variations in crystallinity or to variations in micro-morphology. For unmodified binders, any of the performance indicators can be used to relate binder properties to their performance in asphalt mix tests. For polymer modified binders the behavior is more complex, only well selected parameters relate to the behavior observed in the asphalt mix tests, and only if the binders are tested after appropriate thermal preconditions. A detailed discussion is included on the relations between binder parameters and the respective mix tests, and on the importance of thermal history in these relations. Sample preparation recommendations for binder performance testing are also proposed.