# Viability of Cupola Slag as an Alternative Eco-Binder and Filler in Concrete and Mortars
## 2 Materials and Methods
### Characterization of the Materials
#### 2.1.2 Other Mixing Materials  
The chemical composition of the materials used in this study was determined by energy dispersive X-ray spectroscopy (EDX), the results of which are shown in Table 2.  
Hydraulicity is defined as the ability of a compound to harden as a result of chemical reactions with water to obtain calcium silicates and calcium aluminate hydrates. A first  
Figure 5: Infrared spectrum of cupola slag.  
Figure 6: Micrograph of a cupola slag particle at two different scales: low (**a**) and high level of magnification (**b**).  
approximation to the pozzolanicity of the material can be obtained by the hydraulicity index (HI) [26], defined according to the expression:  
\[\text{HI}=\frac{\text{\%Al}_{2}\text{O}_{3}+\text{\%Fe}_{2}\text{O}_{3}+\text{ \%SiO}_{2}}{\text{\%CaO}+\text{\%MgO}} \tag{1}\]  
The hydraulicity index obtained for OPC is 0.4, while that obtained for cupola slag is 2, which shows the high hydraulicity of this compound. The GGBS shows, in the literature, SiO\({}_{2}\) values typically 10% lower, and CaO values around 7% higher than that of the cupola slag [27]. The rest of the components are in a similar proportion, so a slightly higher hydraulicity would be expected in the case of the cupola slag. This difference in composition is due to the fact that blast furnaces melt and reduce iron minerals, while cupola furnaces melt mainly material from blast furnaces and scrap metal.  
Table 3 shows the real density values, following the indications of the Spanish standard UNE 80103 standard [28] for cement testing. The same table shows the Blaine specific surface, for all admixtures and cement used, by application of the EN 196-6 standard [29]. In the comparison between cement and ground cupola slag, it is observed that the latter has a density 7% lower, and a fineness 13% lower. This value, which proportionally influences the speed of hydration reactions, gives an initial advantage to cement.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Unit** & **Limit Value** & **Obtained Value** \\ \hline Conductivity & \(\mu\)S/cm & - & 72.8 (20 \({}^{\circ}\)C) \\ Acidity & pH & - & 10.41 (21.6 \({}^{\circ}\)C) \\ Chemical oxygen demand & mg/kg m.s. & 500 & \textless{}50 \\ Chlorides & mg/kg m.s. & 800 & \textless{}50 \\ Phenols & mg/kg m.s. & 1 & \textless{}1 \\ Total solid solved & mg/kg m.s. & 4 & 480 \\ Sulfates & mg/kg m.s. & 1000 & 60.4 \\ Antimony & mg/kg m.s. & 0.06 & \textless{}0.01 \\ Arsenic & mg/kg m.s. & 0.5 & \textless{}0.02 \\ Barium & mg/kg m.s. & 20 & \textless{}0.10 \\ Cadmium & mg/kg m.s. & 0.04 & \textless{}0.01 \\ Copper & mg/kg m.s. & 2 & \textless{}0.17 \\ Total chromium & mg/kg m.s. & 0.5 & \textless{}0.06 \\ Mercury & mg/kg m.s. & 0.01 & \textless{}0.02 \\ Molybdenum & mg/kg m.s. & 0.5 & \textless{}0.20 \\ Nickel & mg/kg m.s. & 0.4 & \textless{}0.08 \\ Lead & mg/kg m.s. & 0.5 & \textless{}0.12 \\ Zinc & mg/kg m.s. & 4 & \textless{}0.55 \\ Selenium & mg/kg m.s. & 0.10 & \textless{}0.10 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Results of the cupola slag leaching test.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Material** & **Fe2O3** & **CaO** & **SiO2** & **Al2O3** & **MgO** & **MnO** & **Cr2O3** & **TiO2** & **Na2O** & **SO3** & **K2O** & **Others** \\ \hline Diabase & & & & & & & & & & & \\ sand & 13.7 & 11.1 & 46.5 & 13.6 & 12.4 & - & - & - & 2.8 & - & - & - \\ Silica sand & - & - & 96.0 & 4 & - & - & - & - & - & - & - \\ Cupola slag & 6.3 & 30.0 & 43.6 & 13.6 & 2.1 & 2.8 & - & 0.5 & - & - & - & \textless{}0.5 \\ limestone & - & 100 & - & - & - & - & - & - & - & - & - \\ Fly ash & 7.0 & 6.1 & 55.0 & 20.4 & 2.6 & - & - & 0.9 & 1.2 & 4.0 & 2.0 & - \\ CEM I 52.5 & 3.4 & 66.6 & 17.8 & 4.8 & 1.3 & - & - & 0.2 & - & 4.5 & 0.8 & - \\ R & & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Composition in oxides of the materials used (% wt.).