Ranking the Rheological Response of SBS- and EVA-Modified Bitumen Using MSCR and LAS Tests

The main objective of the study was to characterize the fatigue and rutting behavior of polymer-modified asphalt binders, by determining the effect of temperature and stress/strain levels on the results of multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) test. The modifiers included styrene butadiene styrene (SBS) and ethylene vinyl acetate (EVA). These effects were quantified by means of nonrecoverable creep compliance ($J_{\mathrm{nr}}$) and percent recovery ($R$) values in MSCR, and fatigue power law model Parameters $A$ and $\alpha$ in LAS test. The results were also compared with the conventional binders, VG 10 and VG 30. A new methodology has been proposed to rank the binders based on different sets of priority given to various test parameters. From the laboratory investigation it was found that EVA-modified binder showed good performance at high temperatures, with the lowest $J_{\mathrm{nr}}$ values, but was found to be highly strain susceptible at intermediate temperatures. Stress levels had significant effect on the $R$ values in the MSCR test. The fatigue life for all the binders in the LAS test was found to be sensitive to the values of $A$ and $\alpha$. Conventional binders were found to have higher fatigue life than EVA-modified binders at intermediate temperatures and higher strain levels. SBS-modified binder performed well in both rutting and fatigue. The proposed methodology for evaluation of ranking can be successfully used to choose the best performing binder from a set of different binders based on the priority given to different tests. The usefulness of the methodology has been demonstrated using a suitable example.