Characterization of Fatigue Resistance of Warm Mix Binders Using Linear Amplitude Sweep Test

Fatigue failure in asphalt pavements occur due to the accumulation of damage under repeated traffic loading. Fatigue cracks generally occur within the binder phase of the asphalt mixture. Hence the specifications for properties related to fatigue resistance of asphalt binder become an important screening tool to select binders that are not inherently susceptible to fatigue under given environmental and traffic conditions. The Current Superpave Performance Grading (PG) specifications use parameter |G*|.·sinδ of asphalt binder to assess the fatigue susceptibility of asphalt mixes. These specifications do not accurately characterize the fatigue resistance of asphalt binders because |G*|.·sinδ is determined by applying a cyclic loading in the Dynamic Shear Rheometer (DSR) at a very small strain amplitude (1%). In this study, Linear Amplitude Sweep (LAS) test was considered to characterize the fatigue resistance of asphalt binders with warm mix additives. Warm mix asphalt (WMA) is a developing technology that can allow asphalt concrete to be produced at lower temperatures. This paper presents result of a study carried out to investigate the fatigue characteristics of warm-mix asphalt binders using a linear amplitude sweep test. Three warm-mix additives; Sasobit®, Evotherm™ and Rediset® are considered. Viscosity grade (VG 30), Polymer modified binder (PMB 40) and Crumb rubber modified binder (CRMB 60) were selected as base binders for this investigation. Physical and rheological tests were carried out for the characterization of these binders. The LAS test was carried out at 25 °C in a DSR, and the fatigue parameters were calculated from stress–strain plots. Test results showed that the changing trend in fatigue life of mixes is more related to the fatigue parameter Nf from LAS test than to |G*|. sinδ values of the binders. It was also observed that most of the warm mix binders have improved fatigue resistance at 25 °C in comparison to the control binders. The effect of Rediset® additive was found to be insignificant in the case of VG 30 grade binder only.