# Evaluation of Waste Express Bag as a Novel Bitumen Modifier
## 4 Conclusions  
This paper conducted a series of laboratory tests to characterize and compare the rheological properties of virgin bitumen modified with five different dosages of PE from waste express bags. Some materials experiments were also used to analyze the modification mechanism of the modified bitumen. According to the test data for the three empirical indicators, workability evaluation, Superpave rutting factor test, multiple stress creep recovery test, BBR test, Fourier transform infrared spectroscopy, and fluorescence microscope, the following major findings were obtained.  
The softening point test, PG classification, and MSCR test revealed that WEB can greatly improve the high temperature performance of bitumen as a modifier. The incorporation of WEB additives improved the rutting resistance of virgin bitumen, and the rutting resistance increased with the increase in WEB dosage. This improvement comes from the modification effect by the waste express bags.  
When the percentage of the express plastic bag modifier reached a certain level (\(\geq\)8%), the high temperature performance of WEB-modified bitumen was significantly improved. One reason for this is that the PE particles combined to become a bigger structure. The second reason is that the phase angle of the bitumen decreased with the temperature increase. This may be due to the effect of the PE skeleton, which plays an important role in high temperature environments.  
The WEB modifier showed a negative effect on ductility while the data from the BBR test showed that the low temperature performance of WEB-modified bitumen did not decrease when compared with pen 60/70. Therefore, the WEB modifier is more applicable in regions where the lowest temperature is over 0 \({}^{\circ}\)C.  
The WEB additives may decrease the workability to some extent. Therefore, WEB-modified bitumen can be used when the WEB dosage is under 8%.  
The Fourier transform infrared spectroscopy tests showed that the waste express bags did not have a significant chemical reaction during the process of modification. The modification mechanism is mainly physical blending, which means that the WEB-modified bitumen's influence on soil is similar to that of virgin bitumen. It is safe at room temperature.  
Fluorescence microscopy showed that at low WEB dosages, the PE will mix with the virgin bitumen in the form of little particles. At high WEB dosages, the PE will combine together to become a skeleton structure. This may explain why the high temperature performance increased significantly when the additives reached a high level.  
Figure 6: The fluorescence microscope (FM) images: (**a**) Pen 60/70; (**b**) modified bitumen with 6% WEB additive; (**c**) modified bitumen with 8% WEB additive; and (**d**) WEB additives.  
On account of the limited findings of this research, the use of waste express bags as a bitumen additive appears promising. WEB additives have been found to possibly improve the performance of asphalt mixtures in both rutting resistance and low temperature resistance. As plenty of road construction is being planned in China, the use of WEB as a bitumen modifier will surely help with waste management. Further research is needed on WEB-modified asphalt mixture experiments and field performance evaluation. Additionally, many other observation techniques can be used to survey the internal morphology of the modified binders in further study. Finally, WEB-modified asphalt toxicity analysis, recyclability research of WEB and life cost assessment (LCA) study of WEB-modified asphalt pavement can be conducted in the further research.  
Experimental design, C.H.; performing of experiments, Y.L.; formal analysis, Y.L., S.A., C.H and C.W.; writing of paper, Y.L., C.H., M.Y and S.A.  
This research was funded by the National Natural Science Foundation [51578248] and Pearl River S&T Nova Program of Guangzhou [201710010063].  
Support provided by the professor [PERSON] was greatly appreciated.  
The authors declare no conflicts of interest.