Evaluating Effects of Fischer-Tropsch Waxes on Rheology, Rutting, Fracture, and Low-Temperature Properties of Asphalt Binder Containing RAP

Abstract

A high percentage of reclaimed asphalt pavement (RAP) is being used in asphalt mixes to reduce the consumption of new materials and conserve natural resources. It has been reported that when a high percentage of RAP is incorporated in a mix with a new binder, it tends to increase the grade of the virgin binder, making it stiffer. Hence, additives like wax are generally used for asphalt binders to reduce the mixing and compaction temperatures of the mixes. Although many studies have been reported to evaluate the change of viscosity and rheological properties of asphalt binders with the addition of wax, limited work is available in the open literature to investigate the change in high RAP binders with the addition of different waxes. The present study evaluates the effect of two types of waxes on the rheological and fracture performance of control binder (AC30) with and without RAP. The binder samples were prepared with 40% RAP binder and 2% waxes by weight of the base binder. The effect of waxes on various parameters such as viscosity at high temperatures, Superpave performance grade (PG), rutting performance through the multiple stress creep recovery (MSCR) test, fracture performance through the double-edged notched tension (DENT) test, low-temperature PG, and thermal cracking resistance through the bending beam rheometer (BBR) test were studied. The addition of waxes reduced the viscosity, mixing, and compaction temperatures, hence improving the workability of the control binder. The addition of wax also improved the rutting resistance at high temperatures, but the fracture resistance at intermediate temperatures deteriorated. The findings of this study suggest that for AC 30 binder without RAP, Wax-S is a recommended option to enhance performance. Conversely, for AC 30 binder with RAP, Wax-R is preferable, especially in the high- and low-temperature ranges. Moreover, to achieve better performance in AC 30 binder with and without RAP in the intermediate temperature range, Wax-R is a recommended choice.