Unified Fatigue Tests for Asphalt Materials Using Incremental Repeated-Load Permanent Deformation (iRLPD) Methodology

With the increased use of recycled materials in asphalt mixtures, a practical fatigue test is needed for determining effect of additives on durability of asphalt mixtures. The current fatigue tests face many challenges in identifying fatigue performance of asphalt mixtures. This is partly because the test variables are different from the conditions in the field. Pavement Systems has developed iRLPD fatigue test for asphalt mixture, where all test variables and their levels are set to simulate field conditions. There are also companion iRLPD fatigue test for asphalt binder and mastic, which follow the same incremental methodology and measures the same fatigue index as those for the mixtures. Therefore, the fatigue resistance of the binder, mastic, and mixture are well correlated. This paper will discuss the iRLPD test results of the FHWA's accelerated loading facility (ALF) mixtures for a fatigue study. The iRLPD fatigue tests were able to show the difference in fatigue property of extracted binder, recovered mastic, and mixtures of ALF due to use of RAP and RAS. The fatigue indices are also shown to be highly correlated with the number of heavy load repetitions to the first observed cracks in the ALF lanes.