Anti-ageing properties of styrene–butadiene–styrene copolymer-modified asphalt combined with multi-walled carbon nanotubes

This paper presents the findings from a study conducted to evaluate the potential impact of Carbon Nanotubes (CNTs) on the anti-ageing properties of styrene–butadiene–styrene copolymer-modified asphalt (SBS PMA). Ageing Indexes (AIs) of conventional parameters, rheological parameters, and structural changes were employed to capture the changes in asphalt samples before and after ageing. For conventional parameters, AIs of viscosity at 60°C, penetration, and ductility were significantly decreased by the addition of CNTs. Rheological parameters were performed by Master curves and Han curves, including complex modulus (G*), elastic modulus (G′), viscous modulus (G^″), and phase angle (δ). When the amount of CNTs below 0.5 wt.%, the AIs of G* in the low-frequency zone of mater curves for SBS PMA was smaller than the one without CNTs. On the other hand, when the amount of CNTs surpass 0.5 wt.%, the AIs of G* in high-frequency zone of mater curves for SBS PMA was large. CNTs provided unaged SBS PMA with lower slopes of log (G′) versus log (G^″) plots and higher elastic modulus in the terminal region of the plot attributable to the deformation and relaxation of SBS and CNT particles. For structural changes, AI of carbonyl functions and butadiene functions for SBS PMA were larger than that of samples with CNTs; thus, SBS degradation was decreased by adding CNTs. Furthermore, the oxygen-uptake amount of blends combined with SBS and CNTs was lower than that of neat SBS modifiers, demonstrating its important effect on the anti-ageing properties of SBS-modified asphalt.