# Viability of Cupola Slag as an Alternative Eco-Binder and Filler in Concrete and Mortars
## 2 Materials and Methods
### Design and Testing Methodology  
#### 2.2.1 Mix Design  
As already explained, in this study, there are two experimental phases. The first phase consists of comparing the properties of mortars that incorporate cupola slag with mortars that use other admixtures. The second phase consists of checking how different replacements of cupola slag by Portland cement affect standard mortars.  
The manufacturing of standard mortars, incorporating different admixtures, was carried out by manufacturing three mixes that use the same amount of fly ash (FA), limestone filler (LF), and cupola slag (CS) to be able to compare the effect of the cupola slag with that of two of the most common admixtures. To compare only the effect of the admixture, the same amount of CEM I 52.5 R, diabase sand (high quality sand) silica sand (because the diabase sand lacks fines), and 2% plasticizer additive (CEM% wt.) were used. The optimal amount of additive was thoroughly analyzed, since it is the key factor in workability [30]. The only parameter that varies between the three mixes is the w/c ratio, which has been established at 0.43 for the reference mortar (LF) and has been modified for the FA and SC mix to obtain the same consistency. In this way, it has been possible to make a comparison of the mechanical properties of mortars at different ages.  
The manufacture of standardized mortars incorporating different levels of cement replacement was carried out by manufacturing four mixes that use the same amount of silica sand and water. Only the amount of CEM I 52.5 R has been varied, applying ground cupola slag replacements of 0%, 10%, 20%, and 30% (CEM% wt.), obtaining the mixes M-0%, M-10%, M-20%, and M-30%, respectively. In this way, a comparison of the slump and the mechanical properties at different ages can be made. All the mix proportions used in this study were produced following the specifications of EN 196-1 [31] and the proportions appear in Table 4.  
The mortars were mixed in a standard planetary mixer. The mixing method for all of the mortars produced consists of a first phase of mixing the cement (plus cupola slag or admixture if applicable) with water for 30 s at slow speed, 30 s incorporating the sands at slow speed, 60 s at high speed, 90 s with the mixture at rest, and 60 s at fast speed. Standard models (EN 196-1) were used to manufacture 160 \(\times\) 40 \(\times\) 40 mm specimens. The mortars,  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Material** & **FA** & **LF** & **CS** & **M-0\%** & **M-10\%** & **M-20\%** & **M-30\%** \\ \hline Diabase & 435 & 435 & 435 & - & - & - & - \\ sand & 390 & 390 & 390 & 1450 & 1450 & 1450 & 1450 \\ Cupola slag & - & - & 200 & - & 41.8 & 83.6 & 125.5 \\ Limestone & - & 200 & - & - & - & - & - \\ filler & - & 200 & - & - & - & - & - \\ Fly ash & 200 & - & - & - & - & - & - \\ CEM I 52.5 R & 450 & 450 & 450 & 450 & 405 & 360 & 315 \\ Water & 211.5 & 193.5 & 180 & 225 & 225 & 225 & 225 \\ w/c ratio & 0.47 & 0.43 & 0.4 & 0.50 & 0.60 & 0.70 & 0.80 \\ SP & 9 & 9 & 9 & - & - & - & - \\ \hline \hline \end{tabular}
\end{table}
Table 4: Mix proportions of the manufactured mortars (g).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Material** & **Real Density (g/cm3)** & **Blaine Surface (m2/kg)** \\ \hline Diabase sand & 2.89 & - \\ Silica sand & 2.61 & - \\ Cupola slag & 2.89 & 429.4 \\ Limestone filler & 2.65 & 274.1 \\ Fly ash & 2.13 & 400.3 \\ CEM I 52.5 R & 3.11 & 495.7 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Real density and Blaine specific surface of the materials used.  
once manufactured, were covered with plastic wrap in order to avoid moisture loss, and were removed 24 h after mixing. The specimens were cured by immersion in water at a controlled temperature of 20 \(\pm\) 2 \({}^{\circ}\)C for the corresponding curing ages.