Rutting Performance of Warm Mix Asphalt Containing Sasobit

Abstract: In this study, a wax-based warm mix asphalt additive, Sasobit® was used to evaluate its rheological characteristics and rutting performance. Various rheological tests (Such as time sweep, multiple stress creep and recovery, dynamic modulus master curves) were conducted on PG 64-22 and PG 76-22M (polymer modified binder) asphalt binders with and without Sasobit®. An asphalt pavement analyzer was used to conduct rutting susceptibility test. Aging of Sasobit® modified asphalt binder was evaluated by extraction using rotary evaporator. Evaluation of rutting factor G*/sinδ indicates that addition of 1%, 2% and 4% Sasobit® increases rutting resistance. However, evaluation of phase angle indicates that at one grading higher temperature of PG 76-22M, there exists an optimum percent of Sasobit® between 2% and 4% above which rutting resistance will start decreasing. Therefore, it can be concluded that if rut test is performed higher than grading temperature, an overdose of Sasobit® will increase rutting susceptibility. A total of 60 samples were tested using an APA. It was found in this study that 2% Sasobit® reduced rutting susceptibility of Sasobit® modified hot mix asphalt. This finding was verified with higher asphalt content mixes. The fact that Sasobit® reduced rutting susceptibility of HMA was further verified with higher air void mixes. Sasobit® modified WMA mixed at 143 °C and compacted at 110 °C showed better rutting resistance than HMA. Sasobit® modified asphalt mixes prepared at 133 °C and 110 °C also reduced rutting susceptibility. A multiple variable regression rutting model using 60 samples were developed that predicted rutting depths with coefficient of determination of 0.89. Statistical analyses showed that Sasobit® reduced rutting resistance at 5% level of significance. Finally, from aging evaluation of extracted asphalt binders, it can be observed that aging indices of Sasobit® mixes are lower than without Sasobit® mixes. This indicates that Sasobit® mixes do not age as much as without Sasobit® mixes.