Relating asphalt binders response to LAS and LAOS tests at intermediate temperatures

This study is an attempt to quantify the nonlinear rheological behavior of four different asphalt binders using linear amplitude sweep (LAS) test and large amplitude oscillatory shear (LAOS) test at intermediate temperatures (10 degrees C, 20 degrees C, and 30 degrees C) in unaged (UA) and short-term aged (STA) conditions. Additionally, the present study also relates the response of the asphalt binders under increasing strain amplitude, obtained from both test methods. LAS test results indicated improvement in the fatigue life of asphalt binders with an increase in temperature. The effect of ageing on fatigue life was found to be binder dependent. Lissajous-Bowditch (LB) plots and higher-order harmonic ratio I-3/I-1 were found to be imperative analysis procedures to study the LAOS test results. The effect of instrument inertia at low strain and higher frequency, along with the deterioration of the binder at high strain amplitudes, led to distorted stress-strain LB curves, which resulted in ambiguous values of strain stiffening ratio S. It was found that I-3/I-1 can be appreciably correlated with the fatigue life N-f obtained from LAS test using the relationship N-f = 0.2x(I-3/I-1)(-1.42). The relationship validated in the study is found to be independent of temperature, type of binder, and ageing condition.

Automated summary

This study aims to quantify the nonlinear rheological behavior of four different asphalt binders using LAS and LAOS tests at different temperatures. The results showed that an increase in temperature improved the fatigue life of the asphalt binders, with the effect of ageing being binder dependent. Analysis of LB plots and I-3/I-1 ratio were found to be important for studying LAOS test results.