Coupled effects of warm mix asphalt (WMA) additives and rheological modifiers on the properties of asphalt binders

Asphalt pavements, as an essential element affecting the economic vitality of the countries, are widely used to construct the highways and expressways. Severe climate conditions and traffic loads can influence the service life of asphalt pavements and lead to distresses such as thermal cracking and rutting. Various types of modifiers are used in asphalt industry to enhance the resistance of the pavements to these distresses. Although these modifiers improve a wide range of physical and rheological properties, they increase the construction temperatures, leading to increased energy usage and greenhouse gas emissions. The warm mix asphalt (WMA) technologies provide several techniques and additives to reduce the construction temperature of asphalt pavements and decrease the required energy and air pollution in construction phase. This research aims to investigate the influence of Sasobit and Evotherm M1, as two of the commonly used WMA additives, on the performance of unmodified and modified binders. Three types of modifiers (i.e., polyphosphoric acid (PPA), styrene-butadiene-styrene (SBS), and ground tire rubber (GTR)) were used to modify the binders. The influence of modification on the performance of binders was evaluated through some conventional tests such as viscosity, softening point, and penetration grade. Moreover, the performance grading (PG) tests were conducted at a broad range of service conditions. The results indicate that, with some slight variations, the effects of WMA additives on rheological properties have insignificant dependency on the type of modification. Overall, Sasobit increases the stiffness of binders while Evotherm M1 shows negligible effects on the stiffness properties.