# Effect of Micro-Silica Addition into Electric Arc Furnace Steel Slag Eco-Efficient Concrete
## 2 Materials and Methods
### Materials
#### 2.1.2 Aggregates  
In this research, natural limestone aggregates according to standard ASTM C136M-19 Test Method for Sieve Analysis of Fine and Coarse Aggregates [28] have been used. Physical properties of consumable aggregates are density according to standard ASTM C127-15 Test Method for Relative Density (Specific Gravity) and Absorption of Coarse Aggregate [29] and water absorption according to standard ASTM C70-20 Test Method for Surface Moisture in Fine Aggregate [30]. Tables 2 and 4 and also Figure 1 show the results of natural aggregate and EAFS grading analysis. The maximum size of aggregate used is 19 mm in accordance with the requirements of Standard ASTM C33M-18 Specification for Concrete Aggregates [31]. The porosity of natural aggregates is also reviewed by Standard ASTM C29 Test Method for Bulk Density (\"Unit Weight\") and Voids in Aggregate [32]. The natural aggregates were acquired from a local source. The sand used for this research was obtained from Isfahan (Iran), a local source, and Industrial waste slag was obtained from a local steel plant called Isfahan Steel Co. According to Standard BS 1047 Specification for air-cooled blast furnace slag aggregate for use in construction [33], all EAFS in the open environment (Bank slag) and slowly cooled to find crystalline shape and are suitable for use as aggregate. Figure 2 shows aggregate sizes used.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Sample** & **SiO2** & **Al2O3** & **Fe2O3** & **CaO** & **MgO** & **SO3** & **K2O** & **Na2O** & **C3A** & **P2O5** & **TiO2** \\ \hline Cement & 22.00 & 5.00 & 3.82 & 64.00 & 1.90 & 1.50 & 0.49 & 0.25 & 6.50 & - & 1.00 \\ EAFS & 25.80 & 4.90 & 31.80 & 28.60 & 6.30 & - & - & - & - & 0.26 & 0.90 \\ Microsilica & 94.55 & 1.32 & 0.89 & 0.26 & 0.18 & - & 0.21 & 0.15 & - & 0.17 & 0.04 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Chemical properties of materials (%wt.).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Name** & **Type** & **Appearance** & **Density (g/cm3)** & **pH** & **Physical State** & **Ionic Nature** \\ \hline MLS & polycarbonate & dark green & 1.03 & \(7\pm 1\) & liquid & anionic \\ \hline \hline \end{tabular}
\end{table}
Table 3: Technical specifications of the Superplasticizer.  
Figure 1: Grading chart of natural aggregate and EAFS aggregate (0–5 mm), (5–12 mm), (12–19 mm).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Aggregate** & **Size (mm)** & \multicolumn{5}{c}{**Property**} \\ \hline  & & **Apparent Density** & **Real Density** & **Water Absorption** & **Porosity** & **Los Angeles** \\  & & **(g/cm3)** & **(g/cm3)** & **(wt.\%)** & **(vol.\%)** & **(\%)** \\ \hline \multirow{3}{*}{Limestone} & 0–5 mm & 2.60 & 2.63 & 1.35 & 4.78 & 22.05 \\  & 5–12 mm & 2.62 & 2.67 & 1.53 & 4.70 & 20.47 \\  & 12–19 mm & 2.62 & 2.67 & 1.32 & 4.00 & 19.20 \\ \hline \multirow{3}{*}{EAF Slag} & 0–5 mm & 3.65 & 3.27 & 2.5 & 10.89 & 18.14 \\  & 5–12 mm & 3.55 & 3.36 & 2.2 & 12.10 & 16.70 \\ \cline{1-1}  & 12–19 mm & 3.57 & 3.37 & 2.2 & 12.30 & 15.40 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Physical and properties of aggregates.