ABSTRACT
In general, asphalt binders are characterized in a low strain regime where the response is linear viscoelastic (LVE). The shear stress response is independent of the strain amplitude within the LVE limit and the frequency of the response is same as the applied frequency. However, when the asphalt binder is subjected to strains beyond the LVE limit, the response becomes nonlinear. In this regime, the response is stress or strain level dependent and may be comprised of higher order frequencies that contribute to the overall nonlinear response. In this study, a crumb rubber modified asphalt binder is tested at large strains of 30%, 40% and 50% at an applied frequency of 0.5 Hz and testing temperature of 30°C. The total stress response is analyzed using Fourier transform rheology. It is found that there is an appearance of higher harmonics in the total stress response. The contribution of higher harmonic is characterized as a function of strain amplitude and it appears to follow a sigmoidal fit of strain amplitude.
