Impact of Block Ratio, Polymer Architecture, and Soft Segment Structure on Modified Asphalt Rheological Performance

This study investigates the impact of styrenic triblock copolymer (STC) modifiers with different block ratios, polymerization methods, and soft segment structures on the microstructure and rheological properties of modified asphalt. Six commonly used STCs were selected, and modified asphalt was prepared using a rapid quenching method without stabilizers, ensuring no phase separation. These samples underwent laser confocal microscopy, temperature sweep, multiple stress creep recovery, linear amplitude sweep, and bending beam rheometer tests. The findings are as follows: Based on the characteristics of different STC types, it is observed that modifiers with higher block ratios and crystallinity are more challenging to disperse uniformly in modified asphalt. However, the presence of methyl side chains enhances the dispersion uniformity of the modifier in asphalt. Additionally, star-shaped modifiers exhibit weaker dispersion uniformity compared to linear ones. Among them, the styrene-butadiene-styrene (SBS) modified asphalt with a block ratio of 3/7 demonstrates the highest composite modulus and maximum creep recovery, showcasing superior high-temperature performance. Star-shaped SBS-modified asphalt excels in high-temperature performance and exhibits better stress relaxation at low temperatures, but it has a lower fatigue life compared to linear SBS. Styrene-ethylene-butadiene-styrene modified asphalt exhibits the maximum modulus but the poorest elastic recovery performance. Styrene-isoprene-styrene modified asphalt has the minimum modulus and fatigue life but demonstrates optimal elastic recovery.