Several fatigue evaluation methods are available to evaluate the durability of bituminous materials. In some cases, the test results may provide poor correlation with the true fatigue performance, especially when additives with complicated components are incorporated. This study aims to characterize the fatigue behavior of different warm asphalt rubber (WAR) specimens modified by both crumb rubber and warm mix asphalt (WMA) additives, and to validate the feasibility of binder and mortar fatigue tests on WAR. Three WARs with organic, chemical, and foaming additives were prepared. G*sin δ and liner amplitude sweep (LAS) tests (on both binders and liquid phases), and the shear fatigue test (on mortars) were performed. The four-point bending beam (4PB) test was used as reference to validate results of binder, liquid phase, and mortar tests. Test results indicated that the fatigue performance of virgin bitumen is obviously improved by crumb rubber. The selected organic additive contributes to superior fatigue resistance, whereas WARs with foaming and chemical WMA modifiers performed more poorly than asphalt rubber in relation to fatigue, but still much better that the non-rubberized samples. Finally, it is noted that for the rubberized bituminous specimens, LAS evaluation for asphalt binder and the shear fatigue test for asphalt mortar provide same prediction as the 4PB test, whereas other tests give inconsistent results. Therefore, it is suggested to use the 4PB test on mixture, the LAS test on binder, and the shear fatigue test on mortar for fatigue performance characterization of bituminous specimens containing crumb rubber particles. Further validation of the above findings on field specimens is suggested.
Fatigue Resistance Characterization of Warm Asphalt Rubber by Multiple Approaches
