Evaluation of aging impact on rheological and chemical characteristics of crumb rubber-modified warm asphalt binders.

Asphalt pavements are consistently subjected to environmental and loading conditions that affect their durability, such as oxidative aging. Modification of the pavements assists in reducing the aging-induced stiffness. One of these solutions is crumb rubber (CR)-modified warm mix asphalt (WMA) binders. This study aims to assess the long-term performance and effects of aging on CR-modified WMA binders through a series of physical, rheological, and chemical tests. 2% and 4% of Sasobit, a wax-based additive, and 1.5% and 3% of Zycotherm, a nano-based chemical additive, with 10%, 15%, and 20% CR, were utilized. The binders were aged using a rolling thin film oven (RTFO) and pressurized aging vessel. The unaged and long-term aged asphalt binders were tested. Rheological properties, using master curves and zero shear viscosity, physical properties measured through elastic recovery, along with chemical analysis using Fourier transform infrared (FTIR) spectroscopy, were carried out on the binders before and after aging. Based on the physical and rheological aging indices, Sasobit-modified asphalt binders exhibited superior resistance to aging and rutting compared to Zycotherm-modified binders. Specifically, the Sasobit 4% and 20% crumb rubber blend showed the highest resistance to physical aging, while Zycotherm-modified binders demonstrated improved chemical aging resistance. Adding crumb rubber significantly enhanced the stiffness and elasticity of the asphalt binders, further reducing the effects of aging. FTIR analysis confirmed that Sasobit and crumb rubber reduced oxidation and volatile component loss during aging.