Effects of a Wax-Based Warm Mix Additive on Lower Compaction Temperatures

In this study, dynamic viscosity (η'=G" / ω) of a wax-based warm mix asphalt (WMA) additive, Sasobit® (will be called WBA (wax-based additive) in this paper) was measured at temperature ranges from 28°C to 130°C at 6°C interval. Two asphalt binders commonly used in Louisiana, PG64-22 and PG76-22 have been tested with three percentages, 1%, 2% and 4%, of WBA at 10 rad/sec angular velocity and 12% strain with 25mm disc and 0.5mm gap. The dynamic viscosity of asphalt binders at various compaction temperatures were analyzed with respect to field density after different compaction steps. Published field density data for the same binders with same percentages of WBA were used for this verification. In the field, the compaction temperature usually ranges from 155°C to 85°C which includes breakdown and intermediate rolling. Finish rolling normally takes place within a temperature range of 85°C down to 70°C. In this study, the results show that the viscosity of asphalt binders decreases with an increase in percent of WBA at higher compaction temperatures. This trend is reverse at lower compaction temperatures from a point somewhere between 101°C and 104°C for different binders which have a negative effect during compaction of an asphalt mix as a result of suddenly increasing viscosity.