Case study: Evaluation of the effect of extraction temperature on WMA binder containing sasobit additive

The current experimental methods for the extraction and recovery of asphalt binder from asphalt mixtures were designed for hot mix asphalt (HMA); however, it was not ascertained whether or not these methods could also be used for warm mix asphalt (WMA). There are concerns about the inability of current methods to fully extract and recover WMA additives from WMA mixtures, such as Sasobit wax, that can crystallize at room. Therefore, this study investigated the effectiveness of current HMA binder extraction methods for WMAs containing Sasobit additive. An experimental program was designed to evaluate the effect of extraction temperature. The loose mixes for HMA and Sasobit were prepared and subjected to three different aging levels (2 hours, 15 hours, and 5 days) and were extracted at an intermediate temperature (25°C) and an elevated temperature (80°C), respectively. Sasobit can be extracted at 80°C, which was confirmed by the results from the rheological properties test (performance grading, multiple stress creep and recovery test, and frequency sweep test) and a chemical analysis test (Fourier transform infrared spectroscopy test) for the HMA- and Sasobit-extracted binders. Four field Sasobit WMA projects further verified the feasibility of an 80°C extraction temperature for the Sasobit binder. It was also found in this study that the effect of Sasobit on the base binders became less significant after it was subjected to long-term aging in the field.