Rheological, Thermal, and Chemical Evaluation of Asphalt Binders Modified Using Crumb Rubber and Warm-Mix Additive

Abstract

This study evaluates the potential of producing warm-mix asphalt (WMA) using a wax-based additive (Sasobit) in a binder modified using crumb rubber (CR). This binder is formulated for very hot climates and has a grade of PG 82E-16. Three proportions of Sasobit were added to the binder (1%, 2%, and 3%). In the compaction temperature range (130°C-145°C), there was 9% to 16% reduction in viscosity as a result of using 2% and 3% Sasobit. With an increased content of Sasobit, a higher dynamic modulus was identified for the 3% CR+Sasobit binder, and the rutting resistance of the binder also improved. From the fatigue tests, the use of 3% Sasobit caused noticeable reduction in fatigue life. From the nanoscale characterization conducted using Atomic Force Microscope (AFM), an island-type structure was observed for Sasobit-treated binders. This structure could be the wax crystalline phase that improved the stiffness of the binder in nano and macroscales. In addition, thermal analysis was carried out under endothermic and exothermic conditions. The binder's melting temperature reduced and the crystallization temperature increased with the addition of Sasobit. The CR+3% Sasobit binder had the highest percentage of the Carbonyl group, which is associated with binder aging and thus reduced the fatigue life. Overall, it was observed that Sasobit (up to an addition of a 2% dosage) improved the modulus and rutting resistance without degrading the cracking resistance of binders.