Evaluation of physical hardening and oxidative aging effects on Delta T c of asphalt binders

The Delta Tc (ΔTc) is a rheological parameter for asphalt binders, which has been adopted in the past years by many highway agencies in North America for asphalt binder selection. In this study, the effects of the low-temperature physical hardening and oxidative aging on ΔTc are experimentally investigated and analysed. The experimental study is performed on both plain and polymer-modified binders. The results show that both physical hardening and oxidative aging have strong effects on decreasing ΔTc. An approximate linear relationship is identified between ΔTc and rheological parameters, such as the creep stiffness (S) and the m-value. The linear relationship is theoretically explained by analytical derivation. Based on the linear relationship, a graphical method is proposed for interpreting ΔTc using the log(S)-m diagram. By this method, it is found that polymer modification increases the susceptibility of ΔTc to oxidative aging, while it does not significantly affect the susceptibility of ΔTc to physical hardening.