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 (TiO2) 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 TiO2 changed more significantly compared with that of calcium carbonate (CaCO3) and silica (SiO2), which might be due to the smaller particle size of TiO2. Atomic force microscopy (AFM) and Fourier infrared spectrum (FI-IR) analyses demonstrated that the addition of TiO2 resulted in a smoother asphalt surface and a disappearance of the bee structure. Using TiO2 would not accelerate the aging process of asphalt. Moreover, the MD simulation results indicated that a more significant interaction existed between TiO2 and asphalt than that of CaCO3 and SiO2, which resulted in a tighter asphalt molecule and smaller free volume distribution in the TiO2-asphalt system.