Approach for Quantifying the Effect of Binder Oxidative Aging on the Viscoelastic Properties of Asphalt Mixtures

Abstract

Because of the noted influence of oxidative aging on mixture properties and pavement performance, it is becoming imperative to have a more complete understanding of the influence of asphalt binder aging on the viscoelastic behavior of asphalt mixtures. This study proposes a new approach to correlating the oxidative aging of asphalt binder for carbonyl functional groups with the viscoelastic behavior of asphalt mixtures for a continuous relaxation spectrum. The asphalt mixture complex modulus and the carbonyl area for the recovered asphalt binder were measured for mixtures subjected to varying durations of long-term aging in the laboratory. The continuous relaxation spectrum was obtained analytically from the 2S2P1D model of complex modulus of asphalt mixture through the inverse Fourier–Laplace transform approach. A consistent horizontal shift in the continuous relaxation spectrum was observed for all mixtures with the increase in aging duration. However, the shape and the amount of shifting of the spectra were mixture dependent. In particular, mixtures with higher asphalt binder absorption exhibited the greatest shift in the continuous spectra for both unmodified and polymer-modified asphalt mixtures. Good correlations were observed between the carbonyl in asphalt binder and the continuous relaxation spectrum parameters of the asphalt mixture. Such relationships should permit the incorporation of long-term oxidative aging directly into the constitutive equation used in pavement response analyses.