# Influence of Mix Proportions on Rheological Properties, Air Content of Wet Shotcrete--A Case Study
## 2 Materials and Methods  
### Materials  
Table 1 shows the mix proportions. Cement is the ordinary Portland cement (OPC) Po. 42.5, specific gravity 3.14. The F grade fly ash with specific gravity of 2.34 is selected in this test. These two chemical compositions are shown in Table 2. The particle size distribution of cement, fly ash and silica fume was reported in [30]. Please note that these mix proportions are based on previous tests and published literature [2; 31; 32; 33; 34; 35; 36]. Due to the different characteristics of raw materials from different sources, the mix proportion is adjusted according to ACI 506R-16 of \"Shotcrete Guidelines\" [37]. For example, the selected water-binder ratio is slightly higher. In this study, silica fume with specific gravity of 2.21 and specific surface area of 160,000-300,000 cm\({}^{2}\)/g were used. The silica fume is composed of up to 95% SiO\({}_{2}\) and less than 1% CaO, as listed in Table 2. In this study, natural river sand was used as fine aggregate with fineness modulus of 2.66. For coarse aggregate, gravel with a maximum size of 10 mm is used, the fineness modulus is 5.70. The specific gravity of sand and gravel are 2.61 and 2.67, respectively. At the same time, the water absorption of fine aggregate and coarse aggregate is considered to modify the mixed water. The aggregate grading curve conforms to the national standard GB50086-2001. In this study, polypropylene fiber (FI) \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Variable**} & **WC** & **Water** & \multirow{2}{*}{**SR(\%)**} & **Sand** & **FI** & **AEA** & **WR** & **SF** & **FA** \\  & & **(w/b)** & **(kg/m\({}^{3}\))** & & **(kg/m\({}^{3}\))** & **(mm)** & **(\%)** & **(\%)** & **(\%)** & **(\%)** \\ \hline WC45 & Water–binder & 0.45 & 198 & 70 & 1100 & & 0.3 & & \\ WC50 & ratio & 0.5 & 220 & 68 & 1080 & & & & \\ WC55 & (WC) & 0.55 & 242 & 66 & 1070 & & & & \\ WC60 & & 0.6 & 264 & 66 & 1050 & & & & \\ \hline SR50 & Sand ratio & 0.5 & 220 & 50 & 900 & & & & \\ SR60 & (SR) & 0.5 & 220 & 60 & 1000 & & & & \\ SR70 & (SR) & 0.5 & 220 & 70 & 1100 & & 0.3 & & \\ \hline FI6 & Fiber & 0.5 & 220 & 60 & 1000 & 6 & 0.3 & & \\ FI12 & (FI) & 0.5 & 220 & 60 & 1000 & 12 & 0.3 & & \\ FI29 & (FI) & 0.5 & 220 & 60 & 1000 & 29 & 0.3 & & \\ \hline AE0.02\% & Air-entraining & 0.5 & 220 & 60 & 1000 & & 0.02 & & \\ AE0.04\% & agent (AEA) & 0.5 & 220 & 60 & 1000 & & 0.04 & & \\ AE0.06\% & & 0.5 & 220 & 60 & 1000 & & 0.06 & & \\ \hline WR0.3\% & & 0.5 & 220 & 60 & 1000 & & & 0.3 & \\ WR0.6\% & Water reducer & 0.5 & 220 & 60 & 1000 & & 0.6 & & \\ WR0.9\% & (WR) & 0.5 & 220 & 60 & 1000 & & 0.9 & & \\ WR1.2\% & & 0.5 & 220 & 60 & 1000 & & 1.2 & & \\ \hline SF5\% & Silica fume & 0.5 & 220 & 60 & 1000 & & 0.3 & 5 & \\ SF10\% & (SF) & 0.5 & 220 & 60 & 1000 & & 0.3 & 10 & \\ SF15\% & (SF) & 0.5 & 220 & 60 & 1000 & & 0.3 & 15 & \\ \hline FA5\% & Fly ash & 0.5 & 220 & 60 & 1000 & & & 5 \\ FA10\% & (FA) & 0.5 & 220 & 60 & 1000 & & & 10 \\ FA15\% & & 0.5 & 220 & 60 & 1000 & & & 15 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mixture proportions of fresh wet shotcrete. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Raw**} & \multirow{2}{*}{**SiO\({}_{2}\)**} & \multirow{2}{*}{**AI\({}_{2}\)O\({}_{3}\)**} & \multirow{2}{*}{**Fe\({}_{2}\)O\({}_{3}\)**} & \multirow{2}{*}{**CaO**} & \multirow{2}{*}{**MgO**} & \multirow{2}{*}{**SO\({}_{3}\)**} \\
**Materials** & & & & & & & \\ \hline Cement & 19.5 & 6.45 & 3.08 & 57.57 & 1.21 & 2.01 \\ Fly ash & 43.64 & 25.39 & 4.19 & 5.62 & 0.84 & 0.28 \\ Silica fume & 95 & 1.1 & 0.8 & 0.3 & 0.6 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Chemical compositions of cement and fly ash (unit: %). with specific gravity of 0.93 was used. The fiber diameter range was 18-48 \(\upmu\)m, and the fiber content in shotcrete was 0.9 kg/m\({}^{3}\). The tensile strength and elastic modulus of the fiber are more than 500 MPa and 3850 MPa, respectively.