Effect of Photocatalysts Modification on Asphalt: Investigations by Experiments and Theoretical Calculation

The application of photocatalysts on pavement engineering to degrade automobile exhaust has become a hot topic for researchers. However, the effect of photocatalysts on pavement materials has not been fully investigated. The primary purpose of this study is to explore the effect of a typical photocatalyst titanium dioxide (${\mathrm{TiO}}_2$) on the chemical structure and properties of asphalt through laboratory experiments and molecular dynamics (MD) simulation. Performance tests indicated that the physical properties of asphalt modified by ${\mathrm{TiO}}_2$ changed more significantly compared with that of calcium carbonate (${\mathrm{CaCO}}_3$) and silica (${\mathrm{SiO}}_2$), which might be due to the smaller particle size of ${\mathrm{TiO}}_2$. Atomic force microscopy (AFM) and Fourier infrared spectrum (FI-IR) analyses demonstrated that the addition of ${\mathrm{TiO}}_2$ resulted in a smoother asphalt surface and a disappearance of the bee structure. Using ${\mathrm{TiO}}_2$ would not accelerate the aging process of asphalt. Moreover, the MD simulation results indicated that a more significant interaction existed between ${\mathrm{TiO}}_2$ and asphalt than that of ${\mathrm{CaCO}}_3$ and ${\mathrm{SiO}}_2$, which resulted in a tighter asphalt molecule and smaller free volume distribution in the ${\mathrm{TiO}}_2\text{-}\mathrm{asphalt}$ system.