Evaluating Premixing Effects on the Rheological Properties of the Polymeric Bitumen Containing Paraffin Wax and Nanoclay

The effects of various polymeric additives and nanoparticles on bitumen have been widely studied. In some cases, although additives improved the bitumen properties, the specimen preparation conditions were very difficult and sometimes it was only possible at a laboratory scale. Therefore, effort has been made in this research to simplify the process and modifying mixture through making changes in the specimen preparation process. Research has shown that using styrene-butadiene-styrene polymer and nanoclay in bitumen improves its properties, and it can be said that they nicely overlap each other to complement their weak points. The main hypothesis of this research is that by using a premixing method to prepare a mixture of additives with an internal mixer, the distance between plates of nanoclay will increase, which can reduce the steps and time of adding materials to bitumen in the high shear mixer. Moreover, using this method not only facilitates the specimen preparation but also enhances the rheological properties and the way the materials are dispersed in the bitumen. The properties of the specimens prepared by two methods (premixing and conventional) were studied and compared using classical tests (penetration, softening point, and ductility) and multiple stress creep recovery (MSCR) by a dynamic shear rheometer. The results showed that using premixing at a mixing round per minute (rpm) similar to that of the conventional method will improve the bitumen properties, and if rpm is reduced, properties similar to those of ordinary conditions will be achieved and less bitumen aging will occur. In the MSCR test, neat and S-neat specimens do not fall within the MSCR classification range, which is an indication that pure bitumen characteristics are not sufficient to withstand rutting. In general, it was shown that a change in the bitumen modification method had effects on both modification process simplification and the study of performance results. Moreover, further studies on simplifying the mixing process would be helpful for obtaining bitumen with higher performance.