Rheological Properties at Low Temperatures and Chemical Analysis of a Composite Asphalt Modified with Polyphosphoric Acid

This work improved the low-temperature rheological properties of asphalt modified with styrene butadiene styrene (SBS) using an acid modifier, namely polyphosphoric acid (PPA), and investigated the microstructural changes induced by such a modification. Four mass fractions of acid modifier were added into SBS modified asphalt (polymer-modified asphalt, PG 64-28). A bending beam rheometer (BBR) and Fourier-transform infrared spectroscopy (FTIR) were used to obtain the creep stiffness, the m-value, and the microstructure distribution of the modified asphalt binders. Then the fractional viscoelasticity model was used to calculate the damping ratio, xi, and the dissipation energy ratio, omega, of the modified composite asphalt. The creep stiffness and the m-value of the composite asphalt increased, compared with those of SBS-modified asphalt, but this trend was largely affected by temperature. The differences in the calculated results suggest that the addition of the acid modifier to the SBS-modified asphalt enhanced the viscous properties at low temperatures (-30 degrees C <= T <= 0 degrees C). (c) 2020 American Society of Civil Engineers.