Fatigue characterization of bituminous binders

Bituminous binder is a fundamental component in road construction, influencing the durability and lifespan of road surfaces. One of the important distresses in bituminous asphalt mixtures is fatigue failure at intermediate temperatures. Fatigue resistant strongly related to binder properties used in the asphalt mixture. During the last decade, different tests has been defined to investigate the fatigue resistance of binder. Traditionally, time sweep test was used to analyze fatigue properties of binders. However, time sweep challenges with the long duration of testing, the linear amplitude sweep (LAS) test is introduced and proposed by researchers as faster method to estimate the fatigue resistance of asphalt binder. The framework of this study relies on laboratory experiments and various analysis method to investigate the fatigue characterization of different binders by use of dynamic shear rheometer (DSR). In this regard, the LAS test has been chosen as the main protocol to be employed in this research. Materials considered in this study contain two type of neat binders and two different polymer modified binders (PMB). To provide more comprehensive view, these 4 different binders have been subjected to two level of aging (short-term by RTFO and long-term by use of PAV), thus, the investigation covers 12 samples with various properties. Although the standard is required aged samples, the un-aged samples also were tested. The aging of binders expanded the variety of samples and provides the ability to observe the effect of aging in fatigue resistance of binders. This study focuses on the different failure criterions introduced for analyzing LAS test results. The performance predictive accuracy of LAS test is strongly dependent on the selected failure definition. The current standard suggested the peak of shear stress as the failure point, while the peak of pseudo strain energy (PSE) and the 35% reduction in loss shear modulus of binder are also employed as other well-known failure criterions in this research. Result showed coherency between these three failure criterions while the 35% reduction in loss shear modulus showed underestimated results in comparison to the other two failure criterions. Moreover, analyzing results related to the peak of PSE criteria is not always applicable specially in case of testing polymer modified binders. Overall, this study investigates the critical issue of understanding the fatigue properties of bituminous binders to improve road infrastructure sustainability.