# Influence of Mix Proportions on Rheological Properties, Air Content of Wet Shotcrete--A Case Study
## 4 Conclusions
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Requirements**} & \begin{tabular}{c} **WC** \\ **(w/b)** \\ \end{tabular} & \begin{tabular}{c} **Water** \\ **(kg/m3)** \\ \end{tabular} & **SR(\%)** & \begin{tabular}{c} **Sand** \\ **(kg/m3)** \\ \end{tabular} & **FI** & **AEA** & **WR** & **SF** & **FA** \\  & & & **(kg/m3)** & **(mm)** & **(\%)** & **(\%)** & **(\%)** & **(\%)** \\ \hline \hline \multirow{3}{*}{\
\begin{tabular}{c} Pumpability \\ Shootability \\ Compressive strength \\ Optimum mix \\ proportion for wet \\ shotcrete \\ \end{tabular} } & 0.55–0.60 & 220 & 60 & 1000 & 12–29 & 0.04–0.06 & 0.9–1.2 & 15 & 5 \\  & 0.45–0.50 & 220 & 50–60 & 1000 & 12–29 & 0.02–0.04 & 0.3–0.6 & 5–10 & 15 \\ \multirow{3}{*}{
\begin{tabular}{c} Compressive strength \\ Optimum mix \\ proportion for wet \\ shotcrete \\ \end{tabular} } & 0.45 & 220 & 60 & 1000 & 6 & 0.02 & 0.6 & 15 & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Mixture proportions recommended for meeting various shotcrete requirements. and sprayability in a certain range. The increase of yield stress and viscosity is beneficial to build-up thickness. It was found that here are two key factors affecting the fluidity and shotcreting of fresh concrete: free paste effect and ball effect. These two positive effects are conducive to the pumpability of fresh concrete. (3) Through comparative analysis, the effect of silica fume on yield stress is similar to that of fiber and medium sand ratio, and the influence degree of silica fume on plastic viscosity fluctuates around the average level. The effect of silica fume on air content is similar to that of fiber or high sand ratio. The effect of fly ash is basically the same as that of air-entraining agent on rheological properties or air content. The effect of silica fume and fly ash on slump is opposite to that of relative yield stress. (4) Within a given range of variables, silica fume has the greatest influence on the slump and air content of fresh wet shotcrete. The water-binder ratio has the greatest influence on the relative yield stress and plastic viscosity. Finally, we concluded the summary of various factors affecting shotcrete in pumpability and shootability. Mixture proportions recommended for meeting various shotcrete requirements were advised. To study the rheological properties of shotcrete more accurately, we will add more experimental variables in the next step. Conceptualization, J.X. and G.L. ; methodology, X.C. ; formal analysis, N.G. ; investigation, N.G. and G.L. ; resources, G.L. ; data curation, X.C. ; writing--original draft preparation, G.L. ; writing--review and editing, J.X. and X.C. ; funding acquisition, G.L. All authors have read and agreed to the published version of the manuscript  
This research was funded by National Key Research and Development Plan of China, grant number 2017 YFC0805203, National Natural Science Foundation of China, grant number 51974177, 51934004, 51604163, Natural Science Foundation of Shandong, grant number ZR201801280006, ZR2019 QEE007, ZR2019 MEE115, Exchange Projects of the 43 rd Routine Session of the China-Czech Committee for Scientific and Technological Cooperation, grant number 43-4 and Special funds for Taishan scholar project. Not applicable. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.