Evaluation of physical hardening of wax-based warm mix asphalt binders from low-temperature rheological properties

The effects of eight representative commercial waxes on low-temperature properties of asphalt binders after long-term cold storage were investigated using extended bending beam rheometer (ExBBR) test, thermal stress calculation, and statistical analysis. The results showed that the addition of F-T waxes and Montan waxes with typical paraffin characteristics significantly reduced the low temperature rheological properties of asphalt binders after 1 h conditioning. However after 72 h conditioning, all waxes affected the low temperature properties of asphalt binders to varying degrees, especially F-T waxes. The grade loss of 3% F-T wax-doped asphalt binders reached 6.2 degrees C and 4.5 degrees C, respectively. After 72 h conditioning, thermal stresses of wax-doped asphalt binders increased significantly, confirming the effect of physical hardening. Statistical analysis of test results showed that the incorporation of F-T wax, montan wax, naphthenic wax and amide wax significantly increased thermal stresses of asphalt binders, while the incorporation of P (Synthesis of palm wax and polyethylene wax) and L (Amide-functionalized hydrocarbon wax) did not cause significant changes.