Rheological investigation of the effects of tea polyphenols on SBS-modified bitumen before and after short-term aging

Despite the elucidated antioxidant mechanisms of tea polyphenols (TP) in bitumen, their influence on the rheological behavior of SBS (styrene–butadiene–styrene)-modified bitumen remains unclear. To address this gap, TP (0%, 3%, 6%, 9%, and 12%) was incorporated into 4.5% SBS-modified bitumen to prepare five binders, which were then subjected to thermo-oxidative aging, yielding ten samples. Subsequently, a series of rheological tests, including frequency sweep, multiple stress creep and recovery, linear amplitude sweep, and low-temperature relaxation, were conducted to analyze their behavior. Furthermore, high- and low-temperature rheological models were developed for all binders. The results indicate that TP increases the complex modulus and reduces the phase angle of SBS-modified bitumen, thereby enhancing its elastic response, with the optimum effect achieved at a 3% dosage. At this content, under the unaged condition, the SBS/TP composite-modified bitumen also exhibits the greatest fatigue life. Moreover, TP enhances the high-temperature elastic recovery and deformation resistance of binders, as evidenced by increased recovery rate and reduced non-recoverable creep compliance and creep compliance. Notably, TP compromises the low-temperature stress relaxation capability of SBS-modified bitumen, as indicated by higher max stress, shear stress ratio, relaxation time, and model parameter A, along with a lower model parameter n.