Evaluation of methods used in determination of mixing and compacting temperature for neat and modified asphalt binders

Nowadays, due to increasing in traffic volume and load, it is concluded that modified binder should be used in the production of asphalt mixture. The full benefit of using the modified binder can be fully achieved only when the complexity of selecting the mixing and compaction temperature is understood. To estimate these temperatures, different methods are used depending on the viscosity of the bitumen. Furthermore, the viscosity of the bitumen plays a major role in determining these temperatures. High mixing and compaction temperatures have been reported in some polymer modified binders. These high temperatures cause early aging in bitumen, distresses in the asphalt pavements and toxic gases during production. In recent years, warm mix asphalt (WMA) additives have been used to produce lower mixing and compaction temperatures in the production of bituminous hot mixture. In this study, the 50/70 bitumen grade was blended using 2% and 4% styrene-butadiene styrene (SBS) and 3% WMA additive (Sasobit) in a laboratory using a high shear mixer. In order to determine the mixing and compaction temperatures of different modifying composites, the Equi-viscous method proposed by ASTM and the Bitumen Test Data Chart (BTDC) method proposed by Shell were used. According to the results, relatively low mixing and compression temperatures using the BTDC method were obtained for neat and SBS modified bitumen compared to the Equi-viscous method. However, for Sasobit modified bitumen, it's approved the ASTM method is more suitable for the determination of these temperatures.