Usage of Nano-TiO2 or Nano-ZnO in Asphalt to Resist Aging by NMR Spectroscopy and Rheology Technology

Antiaging effects of two inorganic nanoparticles [4% nano-titanium oxide (nano-TiO2) and nano-zinc oxide (nano-ZnO)] on asphalt were investigated by liquid-state nuclear magnetic resonance (NMR) spectroscopy, multiple stress creep recovery (MSCR) tests, and linear amplitude sweep (LAS) tests. The rheology test results showed that rutting and fatigue performance of asphalt binder increased with the addition of nano-oxides, and the addition of nano-ZnO showed improved rutting resistance and fatigue life compared with nano-TiO2. H-1 NMR spectroscopy shows that the aromatic hydrogen ratios and branchiness index (BI) of asphalt decrease significantly after aging. It indicated that some isomerization and dehydrogenation occurred during the aging process. After adding nano-oxides into asphalt binder, the aromatic hydrogen content and the number of branched chains in asphalt susceptible to oxidation are further reduced, which slows the aging degree of asphalt.13C NMR spectroscopy shows that the content of aromatic carbon is the key factor affecting asphalt aging. After original asphalt aging, the aromatic carbon ratios decreased, and adding nano-oxides into asphalt binder, whereas two kinds of nano-oxide-modified asphalt have different trends of aromatic carbon ratios. The antioxidant mechanism of nano-TiO(2 )is to inhibit the loss of aromatic carbon, whereas the oxidation of nano-ZnO-modified asphalt either inhibits the reaction of aging or causes sufficient aromatization to offset the influence of different degrees of asphalt aging.