## 2 Experimental Procedure
### Test Methods  
The compressive and flexural strengths of the concrete subjected to water curing at 20 \(\pm\) 3 \({}^{\circ}\)C were measured at 7, 28, and 91 days of age. The compressive strength was measured using three specimens (\(\updownarrow\)100 mm \(\times\) 200 mm) per concrete mix according to ASTM C39/C39M-20 [14], i.e., Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. The flexural strength was measured using two concrete specimens (100 mm \(\times\) 100 mm \(\times\) 400 mm) per concrete mix according to ASTM C293/C293M-16 [15], i.e., Standard Test Method for Flexural Strength of Concrete. The air-void system properties of hardened concrete (\(\updownarrow\)100 mm \(\times\) 50 mm) at 28 days were measured according to the linear traverse method of ASTM C 457/C457M-16 [16]. A high-resolution flatbed scanner was used to acquire digital images of the concrete cross section. After polishing the cross section, a high-finiteness white powder was applied, and then each pixel corresponding to the cement paste, aggregate, and air void was classified using the Image-Pro analysis software. Based on the image classification, the air content, specific surface area, and spacing factor of each concrete specimen were determined. After fabricating prismatic specimens with the dimensions of 100 mm \(\times\) 100 mm \(\times\) 400 mm, a freeze-thaw resistance test was conducted according to ASTM C666/C666M \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Gmax (mm)** & **Absorption (\%)** & **Fineness Modulus** & **Density (g/cm\({}^{3}\))** \\ \hline S & - & 1.14 & 2.9 & 2.53 \\ G1 & 19 & 0.78 & 6.2 & 2.73 \\ G2 & 32 & 0.93 & 6.8 & 2.75 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Physical properties of aggregates. Figure 1: SEM images of the binders: (**a**) OPC, (**b**) WS, and (**c**) AS. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Mix. Code** & **W** & **C** & **WS** & **AS** & **S** & **G1** & **G2** & **SP \({}^{*}\)** & **AEA \({}^{**}\)** \\ \hline OPC & 157 & 350 & - & - & 645 & 595 & 599 & 0.33 & 0.25 \\ WS40 & 157 & 210 & 140 & - & 632 & 583 & 588 & 0.3 & 0.4 \\ WS35 AS05 & 157 & 210 & 122.5 & 17.5 & 639 & 590 & 594 & 0.5 & 0.5 \\ WS30 AS10 & 157 & 210 & 105 & 35 & 661 & 609 & 614 & 0.55 & 0.5 \\ \hline \hline \end{tabular} \({}^{*}\) wt. of binder (%); \({}^{**}\) wt. of SP (%).  
\end{table} 
Table 3: Mix proportions of concrete (unit kg/m\({}^{3}\)). 15 [17] procedure A using specimens aged for 28 days considering the strength development of concrete. The 3 h-process, in which the standard specimen for temperature measurement is frozen for 1 h from 4 \({}^{\circ}\)C to \(-\)18 \({}^{\circ}\)C and melted for 2 h from \(-\)18 \({}^{\circ}\)C to 4 \({}^{\circ}\)C was set as one freeze-thaw cycle; a total of 300 cycles were performed. The dynamic modulus of elasticity of each concrete specimen was measured every 30 cycles (Figure 2). Then, the relative dynamic modulus of elasticity (RDME) of concrete was calculated as follows. \[\text{RDME}\ =\ \left(\ \frac{\text{n}_{\text{c}}}{\text{n}_{0}}\ \right)^{2}\ \times\ 100\ (\%) \tag{1}\]  
where n\({}_{\text{c}}\) denotes the fundamental transverse frequency after c cycles of freeze-thaw (Hz), and n\({}_{0}\) denotes the fundamental transverse frequency at the start of freeze-thaw (Hz). The durability factor (DF) of concrete was determined after 300 freeze-thaw cycles, as follows. \[\text{DF}\ =\ \ \frac{\text{PN}}{\text{300}}\ \left(\%\right) \tag{2}\]  
where P represents the RDME at N cycles, and N denotes the number of cycles where P is less than 60%; N is set to 300 when P is above 60% after the completion of freeze-thaw. To measure the surface electrical resistivity of the concrete subjected to freeze-thaw cycles, a four-electrode resistivity test was conducted according to the Wenner method (Figure 3) using cylindrical specimens (\(\updownarrow\)100 mm \(\times\) 200 mm) after 0, 90, 210, and 300 freeze-thaw cycles.