Vital role of lower frequencies in the rheological evaluation of SBS modified binders

In this study, the critical role of lower angular frequencies (<= 0.1 rad/s) in analyzing the rheological properties of SBS modified binders (SBS-MBs) have been demonstrated. Frequency sweep measurements were performed from 100 to 0.01 rad/s in the linear viscoelastic region at 60 degrees C. The results show that the rheological signature of the SBS polymer in the binder is primarily observed at lower frequencies (<= 0.1 rad/s). The SBS molecules primarily respond at longer time scales of measurement due to their sluggish dynamics. Hence, the difference among SBS-MBs as a function of SBS content, SBS structure, additives, and short-term aging, increases as frequency decreases. Importantly, the correlation of rheological variables with rut depth improves significantly at frequencies <= 0.1 rad/s. On the other hand, at higher frequencies (>= 10 rad/s), the brittle-like response from the polystyrene segments and the smaller units of the SBS molecule dominate the rheological signal. Therefore at frequencies >= 10 rad/s, the evidence of varying SBS content, SBS structure, additive, and short-term aging was inadequate. Thus, this study reveals that the upper service temperature rheological properties of SBS-MBs are better evaluated and quantified at lower frequencies (<= 0.1 rad/s). For effective grading, quality control, and good correlation with rut depth, a rheological parameter at a frequency <= 0.1 rad/s is essential in polymer modified binders.

Automated summary

This study demonstrates the critical role of lower angular frequencies in analyzing the rheological properties of SBS modified binders. The rheological signature of SBS polymer in the binder is primarily observed at lower frequencies, while at higher frequencies the response is dominated by the brittle-like characteristics of the polystyrene segments and smaller units of the SBS molecule. The correlation of rheological variables with rut depth improves significantly at lower frequencies.