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In order to investigate the dynamic mechanical properties of polyphosphoric acid (PPA) and SBS co-modified asphalt mixtures, uniaxial compression dynamic modulus tests were conducted. The influences of temperature and frequency on the dynamic modulus and phase angle were analyzed. Additionally, dynamic modulus and phase angle master curves were constructed based on the modified Havriliak-Negami (HN) model. A comparative analysis was also performed with SBS-modified asphalt mixtures. The results indicate that both types of asphalt mixtures exhibit similar trends in dynamic modulus and phase angle variations with changes in temperature and frequency. The HN model accurately fits the master curves of dynamic modulus and phase angle for both asphalt mixtures. In comparison to SBS-modified asphalt mixtures, the phase angle of PPA+SBS co-modified asphalt mixtures decreases at -10, 20, and 50 °C, while the dynamic modulus decreases at -10 °C, changes minorly at 20 °C, and increases at 50 °C. Over a wide frequency range, PPA+SBS co-modified asphalt mixtures exhibit increased dynamic modulus and decreased phase angle at high temperatures and low frequencies, while they show decreased dynamic modulus and relatively stable phase angle at low temperatures and high frequencies. These findings suggest that PPA+SBS comodification endows asphalt mixtures superior dynamic mechanical properties. [ABSTRACT FROM AUTHOR]

Considering the characteristics of steel slag, the effective relative density of steel slag was measured by the impregnation method. By the volume substitution method, the asphalt mixtures with different steel slag content were prepared for replacing the coarse aggregates. According to the technical requirements of the ultra-thin friction course, the road performance and the function characteristics of the steel slag asphalt mixture were evaluated. The test results show that with the increasing of steel slag content, the performance indexes of dynamic stability, maximum tensile strain and tensile strength ratio of asphalt mixture are increased with latter decreasing. When the steel slag content is 50%, the comprehensive performance of asphalt mixture is the best. With the increasing of the placement time of test specimens, the high temperature performance index of the steel slag asphalt mixture is increased slightly, while the low temperature crack resistance index and water stability index are decreased. The skid resistance and abrasion resistance of asphalt mixture are significantly improved with the addition of steel slag. The impermeability of the mixture is reduced, while the water seepage coefficient values of several steel slag asphalt mixtures can still meet the requirements of the standard test methods of bitumen and bituminous mixtures for highway engineering (JTG E20—2011). [ABSTRACT FROM AUTHOR]

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