# Fatigue Resistance Characterization of Warm Asphalt Rubber by Multiple Approaches
###### Abstract  
Warm asphalt rubber (WAR) mixture is a sustainable paving material with advantages including waste recycling and noise reducing. A comprehensive understanding of the fatigue performance of WAR specimens is helpful to its wide application. However, research on evaluating the fatigue performance of WAR binder and mixtures is very limited. This paper applies five fatigue analysis approaches to evaluate the fatigue life of WAR samples with three different warm mix asphalt (WMA) additives. The conventional G*sin8, linear amplitude sweep (LAS), indirect tensile fatigue test (ITFT), and four-point bending beam (4 PB) test were conducted based on available standards. In addition, a novel shear fatigue test was performed on WAR mortars. Test results indicated that the incorporation of crumb rubber has a significantly positive effect on fatigue resistance. WAR with chemical and foaming additives exhibited a poorer performance than asphalt rubber (AR), but their fatigue performance was still greatly superior to the non-rubberized samples. Finally, LAS as well as mortar shear fatigue and 4 PB tests provided the same prediction of fatigue resistance, while the results of G*sin8 and the ITFT were inconsistent. It is recommended to use LAS, the mortar shear fatigue test, and the 4 PB test for the fatigue resistance evaluation of rubberized specimens. The validation of the findings with more materials and field performances is recommended.  
multiscale characterization; rheology; mechanical properties; warm asphalt rubber; fatigue behavior +
Footnote †: journal: Applied  
1
Footnote 1: School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510006, China; [EMAIL_ADDRESS] (J.Y.); [EMAIL_ADDRESS] (X.Y.);  [EMAIL_ADDRESS] (D.W.)  
2
Footnote 1: School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510006, China; [EMAIL_ADDRESS] (J.Y.); [EMAIL_ADDRESS] (X.Y.);  [EMAIL_ADDRESS] (D.W.)  
2  
Received: 3 August 2018; Accepted: 27 August 2018; Published: 31 August 2018  
**Featured Application: This work provides reference for selecting appropriate approaches to evaluate the fatigue characteristics of rubberized asphalt specimens containing warm mix asphalt additives or other modifiers.**  
**Abstract: Warm asphalt rubber (WAR) mixture is a sustainable paving material with advantages including waste recycling and noise reducing. A comprehensive understanding of the fatigue performance of WAR specimens is helpful to its wide application. However, research on evaluating the fatigue performance of WAR binder and mixtures is very limited. This paper applies five fatigue analysis approaches to evaluate the fatigue life of WAR samples with three different warm mix asphalt (WMA) additives. The conventional G*sin8, linear amplitude sweep (LAS), indirect tensile fatigue test (ITFT), and four-point bending beam (4 PB) test were conducted based on available standards. In addition, a novel shear fatigue test was performed on WAR mortars. Test results indicated that the incorporation of crumb rubber has a significantly positive effect on fatigue resistance. WAR with chemical and foaming additives exhibited a poorer performance than asphalt rubber (AR), but their fatigue performance was still greatly superior to the non-rubberized samples. Finally, LAS as well as mortar shear fatigue and 4 PB tests provided the same prediction of fatigue resistance, while the results of G*sin8 and the ITFT were inconsistent. It is recommended to use LAS, the mortar shear fatigue test, and the 4 PB test for the fatigue resistance evaluation of rubberized specimens. The validation of the findings with more materials and field performances is recommended.**  
**Keywords: multiscale characterization; rheology; mechanical properties; warm asphalt rubber; fatigue behavior**