# Influence of Fiber Mixing Process on the Cracking Resistance of Cold Recycled Asphal Mixture
## 5 Conclusions  
Four kinds of fiber mixing processes named A, B, C, and D were designed by changing the order of fiber addition. The effect of fiber mixing process on the cracking resistance of CRAM has been evaluated from multiple perspectives in this research. The main findings are concluded as follows:  
1. Based on the results of the semicircle bending test and indirect tensile test, fiber mixing processes have a significant effect on the cracking resistance of CRAM. The CRAM specimens prepared by process C have the largest fracture energy, splitting strength, and fracture work, while the specimens made by process D have the smallest value.
2. For all CRAM specimens, with the increase of freeze-thaw cycles, splitting strength and fracture work of fiber CRAM decrease. However, there is an obvious difference in the reduction rate of splitting strength and fracture work, especially for the specimens under water saturation condition. The specimens made by process C have the smallest reduction rate, which indicates a better resistance to freezing and thawing damage.  
Figure 14: Fiber macro-distribution state in loose CRAM: (**a**) process A; (**b**) process B; (**c**) process C; (**d**) process D.  
Figure 15: Microstructure of fiber in CRAM: (**a**) process A; (**b**) process B; (**c**) process C; (**d**) process D.  
3. According to the analysis of fiber macro-distribution state in loose CRAM, the dispersion state of the fiber is affected by the humidity condition in the mixing environment. In contrast, the best humidity conditions are obtained for fiber dispersion in process C. 4. Based on the SEM observation, an overlapping bridging network structure can be observed in the microstructure of the specimens prepared by process C, which means the mixture could transfer and disperse stress better when it is stressed. This reveals the mechanism of the influence of fiber mixing process on the resistance to cracking of CRAM from the micro level.  
Based on the above results, it is critical to select the appropriate fiber mixing process for the CRAM in engineering practices. Moreover, the influence of the fiber mixing process on the fatigue performance of CRAM needs to be further verified. For this issue, we will study and discuss it in further study.  
Conceptualization: M.W. and C.X.; methodology, M.W.; investigation, T.H. and Y.W.; data curation, T.H.; writing--original draft preparation, M.W.; writing--review and editing, C.X.; funding acquisition, M.W. All authors have read and agreed to the published version of the manuscript.  
The authors gratefully acknowledge the financial support obtained from the Gansu Provincial Science and Technology Plan Project (major science and technology projects) (Project No. 21 ZD8 JA003) and the Fundamental Research Funds for Central Universities (Project No. 3122018C018) of Civil Aviation University of China.  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to requirements of the funder.  
The authors declare that they have no known competing financial interest or personal relationship that could have appeared to influence the work reported in this paper.