Rheological properties and mechanism of fumed SiO₂ modified asphalt

Nano-silica (NS) modified asphalt is satisfactory in mechanical properties but is expensive. Fumed-silica (FS) is also a nanoscale material and the price is only 1/10 of NS. To evaluate the feasibility of FS replacing NS, using 3 wt% original silica (OS), fumed silica (FS), hydrophobic nano silica (MNS) as modifier, the rheological properties of corresponding modified asphalt were studied compared with matrix asphalt (Esso, ES) by the multi-stress creep recovery test (MSCR), linear amplitude scanning test (LAS) and bent beam rheological test (BBR). The results show that the optimal modifier FS has the best effect on the rutting resistance at high temperature and the fatigue resistance at intermediate temperature for asphalt, and the least negative effect on the low temperature performance. The mechanism for these results was explored by SEM, temperature scanning test (TeS), variable temperature infrared spectroscopy (VT-IR), TGA and DSC. The intrinsic primary aggregates of FS and unique ES-hydroclusters system played a key role in the performance of FS-asphalt composite. Therefore, fumed SiO₂ is a cost-effective nano-scale material used to modify asphalt.