Investigating the Rheological Properties of Styrene-Butadiene-Styrene-Based High-Viscosity Modified Asphalt Using Carbon Nanotubes

Styrene-butadiene-styrene (SBS) is currently the most widely used asphalt modifier. However, high-SBS-concentration high-viscosity modified asphalts (HVMA) are characterized by poor flow and storage instability. To make up for the lack of performance of traditional SBS-HVMA, a nano-based high-viscosity composite modified asphalt with excellent performance was developed. Since carbon nanotubes (CNTs) are nanomaterials, they are prone to agglomeration when added to the modified asphalt, and the dispersion effect is poor, which affects the modifier's contribution rate. To better disperse CNTs in the modified asphalt, the nanomaterials were modified, and two new CNT additives were prepared by combining two polymers with CNTs. The appropriate ratio of these two new additives was selected to be further combined with SBS to obtain CNTs/SBS-HVMA. The flow characteristics and anti-aging properties of the three kinds of bitumen in different temperature ranges were studied by taking the common SBS-HVMA and Tafpack super (TPS) high-viscosity modified asphalts (TPS/SBS-HVMA) as comparison samples and by evaluating the road performance of a stone mastic asphalt (SMA-13) mixture. The storage stability, workable performance, rheological characteristics, and aging resistance of three high-viscosity asphalts were analyzed through a segregation test, dynamic viscosity analysis, Brookfield viscosity measurements, bending beam rheometer (BBR) tests, dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) before and after short-term aging. The experimental results showed that CNT/SBS-HVMA exhibited good storage stability and workability. DSR measurements and other rheological tests revealed that TPS/SBS-HVMA had higher low-temperature flexibility than the other modified asphalts, while CNT/SBS-HVMA exhibited good high-temperature resistance, aging resistance, and deformation resistance. Through the verification of asphalt mixture performance, it was found that the high-temperature rutting resistance of CNTs/SBS-HVMA prepared by new CNT additives was 7% and 28% higher than those of SBS-HVMA and TPS/SBS-HVMA, respectively, but the low-temperature performance of CNT/SBS-HVMA was 5% lower than that of SBS-HVMA. This showed that CNT/SBS addition improved the high-temperature performance of the asphalt without a significant negative impact on the low-temperature performance of the asphalt.