Testing plan to examine the effects of multiple axle loads on asphalt fatigue using four-point beam tests

This report presents a testing plan to examine the effect that multiple axle group loads (e.g. tandem, triaxles, etc.) have on the flexural fatigue performance of asphalt, and forms a component of long term Austroads project work. The testing plan proposed uses laboratory test equipment to simulate the application of multiple axle loads on laboratory prepared asphalt specimens. Several similar studies have been undertaken recently, with work in Michigan and Japan indicating that the energy dissipated during a test load cycle can be related to the number of axles within a simulated load group, and that the dissipated energy can be related to the fatigue performance of asphalt test specimens. These studies only simulated the response of asphalt in the direction perpendicular to the direction of travel, where only tensile strains are generated. Strains measured parallel to the direction of travel show the generation of successive cycles of compressive and tensile strains. The strain and stress responses of a series of heavily instrumented pavement structures have been measured in Germany. Data from this study has been made available to the Austroads project team.