## Materials and Experimental Procedures
### Mixing Procedure and Preparation of Testing Specimens  
For the mixing procedure, cement and SF were added to the pan-type mixer of 100-L capacity and dry-mixed for 30 s. First, 50% of water was added and mixed for 90 s. Then, the aggregate was added and mixed for 60 s. SP dissolved in the remaining 50% of the water was added to the mixture and continuously wet-mixed for 180 s. After a 60-s stop period to mix the particles adhered to the walls of the mixer by hand, the concrete mixture was mixed for an additional 120 s. The total mixing time was about nine min. As soon as mixing was completed, the RPC for compressive strength was cast in a 50 mm \(\times\) 50 mm \(\times\) 50 mm cube mold, as required in ASTM C109 [27]. The casting of specimens was completed in two layers. Each layer was taped with a rubber stick and shaken to achieve better compaction. The increased surface of the concrete was removed by a scraper. After casting was done, molds were covered with plastic sheets to prevent moisture evaporation. After 24 h, RPC specimens were demolded and cured in water baths at required conditions (saturated lime solution under 23 \(\pm\) 2 \({}^{\circ}\)C or \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Mixture ID**} & \multirow{2}{*}{**WB**} & \multirow{2}{*}{\begin{tabular}{c} **Coded** \\ **values** \\ **of WB** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **SF** \\ **[\%]** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Coded** \\ **values** \\ **of SF** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Cement** \\ **ks/m\({}^{3}\)** \\ **(m\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **SF** \\ **kg/m\({}^{3}\)** \\ **(m\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Sand** \\ **kg/m\({}^{3}\)** \\ **(m\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Water** \\ **kg/m\({}^{3}\)** \\ **(m\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Total** \\ **Vol. m\({}^{3}\)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **SP** \\ **[\%]** \\ \end{tabular} } \\ \hline
**1** & **0.18 WB-20 SF** & **0.18** & \(-\)**1.41** & **20** & **0** & **1000** & **200** & **903** & **216** & **1.00** & **2** \\  & & & & & **(0.317)** & **(0.090)** & **(0.376)** & **(0.216)** & & & \\
2 & 0.1917 WB-23.54 SF & 0.1917 & \(-\)1 & 23.54 & 1 & (0.308) & (0.103) & (0.359) & (0.230) & & 1.00 & 2.5 \\
3 & **0.22 WB-25 SF** & **0.22** & **0** & **25** & **1.41** & **960** & **240** & **776** & **264** & **1.00** & **1.5** \\
4 & **0.22 WB-20 SF** & **0.22** & **0** & **20** & **0** & **1000** & **200** & **788** & **264** & **1.00** & **1.5** \\
5 & 0.2483 WB-23.54 SF & 0.2483 & 1 & 23.54 & 1 & (0.317) & (**0.090)** & **(0.328)** & **(0.264)** & 1.00 & 1.125 \\  & & & & & & **(0.308)** & (1.00) & (0.291) & (0.298) & & & \\
6 & **0.26 WB-20 SF** & **0.26** & **1.41** & **20** & **0** & **1000** & **200** & **673** & **312** & & \\
7 & 0.2483 WB-16.46 SF & 0.2483 & 1 & 16.46 & \(-\)1 & **1030** & **170** & 716 & 298 & 1.00 & 1 \\
8 & **0.22 WB-155F** & **0.22** & **0** & **15** & \(-\)**1.41** & **1043** & **157** & **802** & **264** & **1.00** & **1.5** \\
9 & 0.1917 WB-16.46 SF & 0.1917 & \(-\)1 & 16.46 & \(-\)1 & **1030** & **170** & **579** & 230 & & \\
10 & 0.18 WB-0 SF & 0.18 & NA & 0 & NA & (0.381) & (0) & (0.403) & (0.216) & 1.00 & 1.5 \\
**11** & **0.22 WB-0 SF** & **0.22** & **NA** & **0** & **NA** & **(0.381)** & **(0)** & **(0.355)** & **(0.264)** & **1.00** & **1.0** \\
12 & 0.26 WB-0 SF & 0.26 & NA & 0 & NA & (0.381) & (0) & (0.307) & (0.312) & 1.00 & 0.5 \\ \hline \hline \end{tabular} Note: 0.18 WB-20 SF refers to 0.18 water-to-binder ratio (WB) and 20% silica fum.  
\end{table} 
Table 2: Mixture proportion of Reactive Powder Concrete (RPC) (kg/m\({}^{3}\)) and response surface method (RSM) values. 40 \(\pm\) 2 \({}^{\circ}\)C) till the age of 3 days, 7 days, 28 days, and 56 days.