Rational Fatigue Limits For Asphalt Binders Derived From Pavement Analysis

摘要

The Superpave specification has some critical gaps, most of them related to the performance characterization of modified binders. This issue is generally recognized by the State Highway Agencies, industry and researchers (1). In 2001 NCHRP 459 (1) report was published, offering a revised system for testing and evaluating asphalt binders based on damage behavior. For fatigue characterization of binders, a new specification parameter was proposed, called Np20. One of the main advantages of the new parameter was the inclusion of the pavement structure in the specification. This paper starts with a review of why G*sinδ has to be replaced by the new parameter Np20. The NCHRP 459 proposal for Np20 was, however, only conceptual and lacked the details required for implementation, specific criteria and limits. The main purpose of this paper is to show how pavement structural analysis can be used to implement the binder fatigue specification parameter Np20. Pavement analysis using a multilayer elastic theory program was used to determine the strain levels in the pavement for six different pavement structures typically used in practice. From those strains, the fatigue life of 19 different binders was calculated. Known relationships between mixture and binder strain, and between mixture and binder fatigue life, were used in the calculations. The results allowed determining the suitability of the 19 binders for different traffic volumes, speeds and pavement structures. Testing conditions (temperature and input energy) for the conditions of Wisconsin and specification limits for Np20 are proposed.