Thermal stress calculation of wax-based warm mix asphalt considering thermorheologically complex behavior

Abstract

The warm mix asphalts which reduce the environmental pollution always show thermorheologically complex behavior under the realistic working conditions (the long-term loading at the low temperature) in the cold region. However, many scholars ignore the thermorheologically complex behavior when calculating thermal stresses. In this paper, the new thermal stresses calculation method considering thermorheological complexity of four wax-based warm mix additives (Fischer-Tropsch (F-T) based wax, fatty acid amides (FAA) based wax, polyethylene (PE)-based wax, and linear aliphatic hydrocarbon (LAH)-based wax) modified asphalt binders were proposed, which was the process of incremental iterative (Named as ‘the incremental method’). The results show that the warm mix asphalt exhibits the thermorheologically complex behavior under long-term loading condition at the low temperature through the tail of the master curve of stiffness modulus, and the thermal stresses considering thermorheologically complex characteristics calculated by the incremental method are greater than that calculated by the traditional Monismith method. Therefore, the incremental method should be used to calculate the thermal stress of asphalt binders under the long-term loading condition instead of the Monismith method, otherwise the cracking risk of the asphalt binder will be underestimated. The wax-based warm mix additives with longer chain molecules and cold storage time can increase the thermorheological complexity more evidently, and the thermal stresses of asphalts with thermorheologically complex characteristics are more sensitive to cooling rate. All in all, the proposed incremental method will provide a supplement to the calculation method of the thermal stresses in the asphalt binder.