## 4 Conclusions  
In this study, TEOS and FAS were prehydrolyzed in MgCl\({}_{2}\) solution containing H\({}_{2}\)O\({}_{2}\) as a blowing agent and then mixed with MgO powder to further hydrolyze and synthesize hydrophobic foamed magnesium oxychloride cement. The properties of cement were characterized and compared to ordinary foamed magnesium oxychloride cement. The results are the following:  
1. Firstly, we pre-hydrolyzed TEOS and FAS in the MgCl\({}_{2}\) solution. When the MgO and the MgCl\({}_{2}\) solutions were mixed, the pH of the system rose to weakly alkaline, which further catalyzed the hydrolysis condensation of TEOS and FAS, and the XPS results demonstrate that the fluoroalkyl chain was successfully introduced into F-MOC. The presence of TEOS made the F-MOC normal pore size distribution curve obtained by adding the same H\({}_{2}\)O\({}_{2}\) foaming agent content thinner than the N-MOC, and the pore structure of the material was more uniform.  
Figure 14: The dehydration rate of F-MOC and MOC (F-MOC and N-MOC bulk density are both around 600 Kg-m\({}^{-3}\), blistering time is 120 Min, the temperature is 30 \({}^{\circ}\)C).  
Figure 13: Moisture absorption rate of F-MOC and MOC with a different bulk density.  
2. The overall hydrophobic F-MOC with a bulk density of 300 kg: m\({}^{-3}\)-1200 kg: m\({}^{-3}\) and a water contact angle of 156\({}^{\circ}\) was prepared by doping with an organosilane. The XRD result and the calculation of the relative content of five-phase show that the five-phase of F-MOC was the main strength phase, as its relative content was only 3.5% lower than that of N-MOC. Based on compressive strength retention, it prevented moisture intrusion and increased its resistance to water. It fundamentally solved the poor water-resistance of the foamed MOC.
3. With decreasing bulk density, although the moisture absorption rate of F-MOC increased, it was less than that of N-MOC. When the bulk density was 300 Kg-m\({}^{-3}\), the moisture absorption rate of F-MOC was 13.3%, while in that of N-MOC, the moisture absorption rate of MOC was as high as 29.5%. In the high-temperature dehydration experiment, the F-MOC mass could be restored to 98.1% of the original mass, while the N-MOC mass could only be restored to 83.2%, indicating that the moisture invading the sample was more evaporated in the form of free water and did not participate in the MOC hydration reaction, effectively preventing the strength loss caused by the collapse of the pore structure caused by hydration.
4. The influence of mechanical polishing and chemical corrosion on the hydrophobic properties of F-MOC show that the composite material has good engineering durability and broad application prospects.  
Conceptualization, R.C. and H.W.; methodology, R.C.; software, S.G.; writing--original draft preparation, J.H.; project administration, R.C. and H.W.; funding acquisition, R.C. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors gratefully acknowledge financial support from National Natural Science Foundation of China (21571024) and Major Special Science and Technology Projects in Qinghai Province (2018-NN-152).  
The authors declare no conflict of interest.