Asphalt binder characterization using waveform-based viscoelastic measures and time-temperature superposition principle under large strains

Abstract

In the United States, currently peak-to-peak oscillatory shear stress-strain data is used in the asphalt binder characterization protocols. This practice necessitates the measurement, usage, and reporting of only peak responses for material characterization and specification even though a sinusoidal waveform is applied. However, in this paper it is argued that with the proliferation of modified binding systems, it is critical to capture and examine the complete waveform data when subjected to both small and large strains. This approach will help properly differentiating between materials. In this study, four modified binders were tested at small and large strain levels while recording the complete response waveform. The recorded waveform data was then used to examine the linear and nonlinear viscoelastic characteristics of these binders. The orthogonal stress decomposition technique was used to delineate elastic and viscous contributions in the nonlinear regime. This study examined the time-temperature dependency under both linear and nonlinear regimes. The time-temperature shift factors obtained from linear regime were effectively applied in the nonlinear regime. Further, all the tested binders showed strain stiffening and shear thinning behavior under most of the testing conditions. This study provides useful insights about the material behavior under nonlinear regime and can serve as a benchmark for further investigation of nonlinear viscoelastic behavior of asphalt binders.