Analysis of asphaltic binders modified with PPA by surface techniques

Samples of unmodified and modified asphalt binders containing 1% polyphosphoric acid were studied. Fourier-transform infrared spectroscopy was used to evaluate the structural indices of the functional groups present in the samples and the results indicated there was a strong interaction between the polyphosphoric acid and oxygenated species. Contact angle measurements indicated that adhesion of the binder to the aggregate depended on the polyphosphoric acid content. Atomic force microscopy was used to relate features observed on the surface of the asphalt binder 50/70, with their local mechanical properties such as stiffness and elasticity. It was observed that the surface of the sample containing 1% polyphosphoric acid provides stiffness values lower than the unmodified asphalt binder.