Rheological and Thermo-Oxidative Aging Properties of Asphalt Modified with a Combination of Sasobit and Linear Low-Density Polyethylene

Research of different asphalt modifiers has been necessary for the attempt to construct durable roads with higher standards. Fischer Tropsch-paraffin wax (Sasobit) has recently attracted considerable attention over polymer modification due to its capacity to lower the energy requirements for asphaltic mix construction. In this study, Sasobit was used to recover the performance as well as the workability of 3 wt% linear low-density polyethylene (LLDPE) modified asphalt. A base asphalt binder with a penetration grade of 50/70 was blended with 3 wt% LLDPE and 3 wt% Sasobit separately and then combined with different Sasobit dosages (1–3 wt%). The performance of modified asphalt binders was evaluated using conventional, rheological, and thermal tests. As a result, it was found that loading Sasobit (1–3 wt%) into LLDPE-asphalt mixture steadily decreased the penetration and ductility at 25 °C from 25 to 12 dmm and 31 to 18 cm, respectively, and softening point increased by 20% indicating improved high-temperature performance. The binder workability and mix temperature were improved since the addition of Sasobit reduced the LLDPE-asphalt viscosity from 0.292 to 0.189 Pa.s (22% less). Sasobit improved the thermo-oxidative aging resistance of the binder by showing less weight variation (less than 0.001%) after the Rolling Thin-Film Oven Test (RTFOT) and high ductility retention (65%). Thermogravimetry (TG) and kinetics analysis results indicated that Sasobit-LLDPE delayed the initial and maximum decomposition temperature by 11 °C and hence increased the thermal stability of modified binders. Thus, the proposed binders are a suitable solution for asphalt pavement construction in regions that encounter high-temperature changes.