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

• Published in: Materials and structures Vol. 55; no. 3
• Main Authors: Pandey, Akanksha, Islam, Sk Sohel, Ransinchung, R. N. G. D., Ravindranath, Sham S.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.04.2022; Springer Nature B.V
• Subjects: Additives; Building construction; Building Materials; Civil Engineering; Engineering; Evaluation; Machines; Manufacturing; Materials Science; Original Article; Polymers; Polystyrene resins; Processes; Quality control; Rheological properties; Rheology; Solid Mechanics; Theoretical and Applied Mechanics; Rutting; MSCR; Polymer modified binders (PMB); Rheology; Angular frequency; Styrene–butadiene–styrene (SBS)
• ISSN: 1359-5997; 1871-6873
• DOI: 10.1617/s11527-022-01922-y

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 °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.