An investigation was carried out on the rutting and fatigue properties of asphalt mixes containing some of the modified binders commonly used in Australia. For rutting, both laboratory wheel tracking and accelerated pavement testing using the ALF (accelerated loading facility) were carried out. For fatigue, testing was limited to laboratory characterisation using the newly developed IPC Beam Fatigue Apparatus. In all testing Class 320 bitumen binder was used as the control mix. Results indicated that modified binders such as Mobil MPlus and Mobilplast RI greatly reduce the level of rutting, the rate of rutting and the sensitivity of rutting rate to temperature. Results also suggest that the laboratory wheel tracking test appears to correlate well with the results of ALF testing. Modified binders such as Mobilfex AG1 and Mobilplast R1 significantly improved the fatigue resistance of asphalt mixes. The density of an asphalt mix affected both the flexural stiffness and fatigue life. A reduction in density equivalent to an increase of 3 percent air voids in a mix resulted in about 25 percent reduction in stiffness and 80 percent reduction in fatigue life. Binder parameters based on dynamic shear rheometry testing gave a fair prediction of relative mix performance for rutting but not for fatigue. (A)
Abstract