Effect of Hierarchical ZnO/PAC Nanosheets on the Rheological Performance of SBS-Modified Asphalt

To improve the rutting resistance and low-temperature cracking performance of polymer-modified asphalt under extreme conditions, hierarchically structured ZnO-loaded porous activated carbon (ZnO/PAC) nanosheets were introduced as a synergistic reinforcing agent for SBS-modified asphalt. The ZnO/PAC hybrids were synthesized via template-assisted carbonization followed by hydrothermal growth, and their effects were evaluated by microscopic characterization and rheological tests, including temperature sweeps, multiple stress creep and recovery (MSCR), and bending beam rheometer (BBR) analyses. ZnO was successfully anchored onto the PAC, forming a three-dimensional flower-like nanostructure. Among the investigated samples, ZPS3 with 3 wt.% ZnO/PAC showed the best overall performance. At 64 °C, the rutting factor increased from 4.2 kPa for the SBS-modified asphalt to 6.8 kPa for ZPS3, representing a ~62% enhancement and indicating markedly improved high-temperature deformation resistance. MSCR results further confirmed the superior rutting resistance of ZPS3, which exhibited the highest recovery and the lowest non-recoverable creep compliance. In addition, BBR results showed that the low-temperature performance grade improved from −12 °C for conventional the SBS-modified asphalt to −18 °C for the ZnO/PAC-modified system. These results demonstrate that ZnO/PAC nanosheets can effectively enhance both the high-temperature rutting resistance and low-temperature cracking resistance of SBS-modified asphalt.