Rheological effects on bitumen of polyphosphoric acid (PPA) addition

The rheological effects of polyphosphoric acid (PPA) on bituminous binders with similar mechanical and chemical–physical properties, but with different chemical compositions, have been investigated. The effects of polyphosphoric acid were studied through traditional bituminous-binder-type characterization tests and via rheological investigations by dynamic and steady shear rheometry. observed that PPA, probably reducing the asphalten aggregate size, extends the range of viscoelastic behavior, moving the transition to a viscous liquid towards higher temperature and, therefore, improving the mechanical behavior for high temperature applications. These effects seem more evident at low PPA concentrations and suggest the potential existence of saturation effects.