# Self-Organizing Maps to Assess the Recycling of Waste in Ceramic Construction Materials
## 2 Materials and Methods
### Ceramic Mixtures Processing  
The methodology used in this work is illustrated in Figure 1. Three different sets of experiments were carried out. A first group of laboratory trial (30 samples) was made in order to determine the viability to obtain suitable pieces at the laboratory conditions. The mixing process of WS (0-40%), FSD (0-40%) and clay (100-60%) (Figure 2) was carried out with a small percentage of water, in a Raimondi Iperbet Jobsite Mixer. Moulding was performed by uniaxial pressing of test-pieces under 10 MPa with a Mignon SS/EA Nanetti laboratory press. Drying and firing of mixtures were performed in a laboratory electric furnace, Hobersal Model 12 PR/300 following the industrial firing cycles: C1-based mixtures (wall bricks and blocks to cover) were fired at 850 \({}^{\circ}\)C for \(\sim\)45 h; C2-based mixtures (roof tiles) were fired at 950 \({}^{\circ}\)C for \(\sim\)35 h, and C3-based mixtures (face bricks) were fired at 1050 \({}^{\circ}\)C for \(\sim\)24 h. Further details can be found elsewhere in [PERSON] et al. [19; 20; 38]. These samples are labelled with a first tag, which means the experimental scale, L (laboratory), the next one corresponds to the type of clay (C1 to C3), and the following the percentage of \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Major Oxide (\%)**} & \multicolumn{4}{c}{**Clay**} & \multirow{2}{*}{**Foundry Sand Dust (FSD)**} & \multirow{2}{*}{**Waelz Slag (WS)**} & \multirow{2}{*}{**Wood Pulp**} \\ \cline{2-2} \cline{5-8}  & **C1** & & & & & & & \\ \hline
**SiO\({}_{2}\)** & 46.55 & 56.35 & 64.22 & 49.48 & 51.02 & 7.15 & 10.73 \\
**Al\({}_{2}\)O\({}_{3}\)** & 15.28 & 16.92 & 16.93 & 17.68 & 12.36 & 3.47 & 6.71 \\
**Fe\({}_{2}\)O\({}_{3}\)****a** & 5.21 & 5.94 & 5.91 & 5.72 & 3.47 & 56.02 & 0.44 \\
**MnO** & 0.07 & 0.07 & 0.06 & 0.03 & 0.09 & 2.60 & 0.02 \\
**MgO** & 2.14 & 4.15 & 0.89 & 1.46 & 2.31 & 3.24 & 1.60 \\
**CaO** & 10.04 & 0.62 & 0.52 & 6.08 & 2.07 & 15.92 & 25.87 \\
**Na\({}_{2}\)O** & 0.59 & 1.11 & 0.58 & 0.67 & 1.93 & 0.78 & 0.16 \\
**K\({}_{2}\)O** & 3.25 & 3.75 & 3.03 & 2.92 & 0.47 & 0.20 & 0.16 \\
**TiO\({}_{2}\)** & 0.63 & 0.82 & 0.83 & 0.69 & 0.39 & 0.18 & 0.206 \\
**P\({}_{2}\)O\({}_{5}\)** & 0.11 & 0.18 & 0.08 & 0.09 & 0.06 & 0.30 & 0.09 \\
**LOI** & 14.50 & 9.77 & 5.78 & 11.98 & 25.61 & \(-\)1.77 & 52.37 \\ \hline \multicolumn{8}{c}{**Trace Elements (ppm)**} \\ \hline
**As** & 40 & 31 & 30 & 13 & 16 & 54 & 2 \\
**Ba** & 704 & 476 & 483 & 510 & 442 & 688 & 148 \\
**Cd** & \(<\)0.5 & \(<\)0.5 & \(<\)0.5 & \(<\)0.5 & 2 & 6 \\
**Cr** & 68 & 95 & 46 & 88 & 18 & 3210 & 65 \\
**Cu** & 33 & 19 & 27 & 21 & 30 & 2300 & 237 \\
**Mo** & \(<\)2 & \(<\)2 & \(<\)2 & \(<\)2 & \(<\)2 & 74 & 3 \\
**Ni** & 42 & 37 & 29 & 46 & 14 & 275 & 30 \\
**Pb** & 36 & 19 & 28 & 26 & 20 & 6570 & 64 \\
**Zn** & 129 & 71 & 139 & 120 & 135 & 43,100 & 134 \\ \hline \hline \end{tabular}  
* Total iron oxide content expressed as Fe\({}_{2}\)O\({}_{3}\).  
\end{table} 
Table 1: Major oxide and trace elements concentrations of the raw materials employed in the manufacture of the ceramic products. Waelz slag (W) and foundry sand dust (F) in the mixture. Reference pieces without waste addition are labelled as LC1 to LC3. In a second development stage, a semi-industrial trial of 22 samples was obtained based on mixtures of C1 clay, WS (0-40%), FSD (0-35%) and a fixed 8% of wood pulp (Figure 2). Mixtures were moulded through a pilot-plant scale extrusion, with a Verdes Model 050C extruder. The obtained prototypes of solid bricks were dried in a muffle furnace at 100 \({}^{\circ}\)C during 24 h and the firing cycle was completed in an industrial furnace, reaching temperatures up to 850 \({}^{\circ}\)C. These samples are labelled with a first tag, which means the experimental scale, S (Semi-industrial), then the type of clay used, C1, and the WS and FSD content was W and F, respectively. Further information can be found in [PERSON] et al. (2014, 2015).