Evaluation of UV aging behaviors of polyphosphoric acid (PPA) modified asphalt and its asphalt mixture

Effects of polyphosphoric acid (PPA) on the ultraviolet (UV) aging properties of asphalt and asphalt mixture were studied. The morphologies of these binders were characterized by FTIR spectra and TG analysis, then the influence of PPA on asphalt and its mixture before and after UV aging were investigated by the physical properties and pavement performances. Results show that the mechanisms of PPA modified asphalt are physical and chemical reactions; both UV aging and PPA additive could prompted the polycondensation of light components in asphalt. Compared with control samples, the introduction of PPA enhances the asphalt properties and intensifies the asphalt mixture performances. Furthermore, the asphalt performance aging variations (penetration aging index, softening point increment, ductility aging index, G*/sinδ aging index) decrease significantly due to the introduction of PPA. This manifests that the effects of UV aging on the behaviors of asphalt and asphalt mixture are restricted by the addition of PPA through inhibiting the increase of carbonyl in the oxidation process.