# Preliminary Study of Recycled Aggregate Mortar for Electric Arc Furnace Dust Encapsulation
## 2 Materials and Methods
### Characterization of Materials
\begin{table}
\begin{tabular}{c c c c c} \hline
**Component (\% Mass)** & **SF** & **Cement** & **NA** & **RCA** \\ \hline SiO\({}_{2}\) & 100.00 & 14.08 & 91.93 & 52.38 \\ Al\({}_{2}\)O\({}_{3}\)\% & – & 3.20 & 3.23 & 7.92 \\ Fe\({}_{2}\)O\({}_{3}\)\% & – & 4.56 & 1.07 & 2.81 \\ SO\({}_{3}\)\% & – & 4.23 & – & – \\ CaO\({}_{3}\)\% & – & 71.98 & 0.71 & 31.2 \\ K\({}_{2}\)O & – & 0.96 & 3.06 & 1.82 \\ MgO\% & – & 0.99 & – & 2.82 \\ Na\({}_{2}\)O & – & – & – & 0.83 \\ Cr\({}_{2}\)O\({}_{3}\) & – & – & – & 0.22 \\ \hline \end{tabular}
\end{table} 
Table 1: Material chemical composition. \begin{table}
\begin{tabular}{c c c} \hline
**Element (\%)** & **EAFD** \\ \hline Zn & 35.45 \\ Fe & 23.53 \\ O & 18.32 \\ Ca & 7.58 \\ Cl & 3.58 \\ Pb & 3.02 \\ Mn & 2.14 \\ K & 1.63 \\ S & 1.22 \\ Mg & 1.17 \\ Si & 1.05 \\ Al & 0.53 \\ Ti & 0.52 \\ Cr & 0.26 \\ \hline Total & 100.00 \\ \end{tabular}
\end{table} 
Table 3: Chemical composition of EAFD. To evaluate the potential contaminating effect of the EAFD, a compliance test was carried out in accordance with the UNE EN 12457-4:2003 standard. This test is used to determine the concentration of heavy metals and anions in the leachate of a waste and allows classifying the waste in accordance with the criteria established by the EU Council Decision 2003/33/EC [19]. The compliance test procedure is described here: the dry mass to be tested was 0.90 kg. A quantity of leachate (deionized water) was added so that a liquid/solid ratio (L/S) of 10 L/kg was established. The mixture was stirred in a tumbler for 24 h at a speed between 5 and 10 revolutions per minute, and then the sample was filtered with 0.45 \(\upmu\)m filters. The liquids from the filtration were analyzed in an ICP-MS (Perkin Elmer ELAN DRC-e) equipped with a system for introducing diluted samples, argon plasma ionization and quadruple ion detection, which has a DRC cell to eliminate interferences. This analysis quantified the 12 heavy metals specified by the European Landfill Directive: Ni, Cr, Sb, Se, Mn, Hg, As, Pb, Cd, Cu, Ba and Zn. In addition, the sulphate, fluoride and chloride anion contents were obtained by ion chromatography according to the UNE-EN ISO 10304-1:2009 standard. Table 4 shows the results obtained in the leaching test. Limit values for the environmental classification of waste according to the EU Council Decision 2003/33/EC [19] are also indicated. In Table 4, it is necessary to highlight the high leaching of Pb in the EAFD sample, since with a pH higher than 12, the Pb is easily mobilized [36; 37; 38; 39]. The EAFD showed a pH value of 13.28 during the UNE-EN 12457-4:2003 compliance test. The pH value of the EAFD depends on the raw material and the additives used in the production of steel; therefore, the pH values of EAFD are highly variable. [PERSON] et al. [40] found slightly lower pH values in five different types of EAFD: 8.2, 9.3, 10.4, 11.0 and 11.4. [PERSON] et al. [16] studied the influence of pH on the leaching of metals from two EAFD. The pH dependence test confirmed minimal Pb release for pH values of 9-11, although when the pH was increased to values higher than 12 the concentration of Pb in the leachate increased significantly.