# Recycling Construction and Demolition Residues in Clay Bricks
## 2 Materials and Methods
### Methods  
These bodies were characterized through the determination of their chemical composition by XRF-WDS (Philips, Cambrige, UK, PW 1480); their mineralogical composition by XRPD (D8 Advance equipped with a LynxEye detector, Bruker, Karlsruhe Germany); and their particle size distribution by X-ray monitoring of gravity sedimentation (SediGraph 5100, Micromerities, Norcross, GA, USA). Nine batches were designed as simple waste plus clay binary mixtures, along with sand + clay taken as the benchmark (SC-GC-MC). Each waste was added in place of sand C as 15%, by weight. The resulting bodies were the S clay (SR1-SR2) and for the M and G clays (MR1-MR2-GR1-GR2). \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Weight \%** & **R1** & **R2** & **C** & **M** & **G** & **S** & **e.u.** \\ \hline \multicolumn{8}{c}{Chemical Composition} \\ SiO\({}_{2}\) & 55 & 36.92 & 83.7 & 56.6 & 53.63 & 51.54 & \(\pm\)0.35 \\ TiO\({}_{2}\) & 0.4 & 0.39 & 0.1 & 0.7 & 0.68 & 0.73 & \(\pm\)0.01 \\ Al\({}_{2}\)O\({}_{3}\) & 10.7 & 8.51 & 8.13 & 17.3 & 13.36 & 14.47 & \(\pm\)0.15 \\ Fe\({}_{2}\)O\({}_{3}\) & 3.11 & 3.41 & 0.46 & 6.9 & 5.26 & 5.91 & \(\pm\)0.07 \\ MnO & 0.07 & 0.08 & - & - & 0.12 & 0.11 & \(\pm\)0.01 \\ MgO & 4.71 & 7.04 & 0.18 & 3 & 2.79 & 4.21 & \(\pm\)0.02 \\ CaO & 11.96 & 24.02 & 1.96 & 3.3 & 8.46 & 7.22 & \(\pm\)0.01 \\ Na\({}_{2}\)O & 1.61 & 0.95 & 1.77 & 0.8 & 1.26 & 1.1 & \(\pm\)0.01 \\ K\({}_{2}\)O & 2.31 & 1.57 & 3.55 & 2.1 & 2.47 & 2.82 & \(\pm\)0.01 \\ P\({}_{2}\)O\({}_{5}\) & 0.16 & 0.11 & - & - & - & 0.13 & 0.15 & \(\pm\)0.01 \\ L.O.I. (1000 \({}^{\circ}\)C) & 9.68 & 16.42 & 0.15 & 9.3 & 11.84 & 11.74 & \(\pm\)0.05 \\ \hline \multicolumn{8}{c}{Mineralogical composition} \\ \hline Quartz SiO\({}_{2}\) & 30\% & 17\% & 58\% & 27\% & 28\% & 32\% & \(\pm\)1 \\ Plagioclase (Na,Ca)(Si,Al)\({}_{4}\)O\({}_{8}\) & 13\% & 7\% & 17\% & 4\% & 9\% & 10\% & \(\pm\)1 \\ Orthoclase KAlSi\({}_{3}\)O\({}_{8}\) & 6\% & 6\% & 19\% & & & & & \\ Calcite CaCO\({}_{3}\) & 13\% & 26\% & 3\% & 6\% & 15\% & 5\% & \(\pm\)1 \\ Dolomite CaMg(CO\({}_{3}\))\({}_{2}\) & 13\% & 24\% & - & - & - & 10\% & \(\pm\)1 \\ Illite-ica K(Al,Mg,Fe)\({}_{2}\) (Si,Al)\({}_{4}\)O\({}_{10}\)(OH)\({}_{2}\)(H\({}_{2}\)O) & 10\% & 3\% & 2\% & 23\% & 23\% & 26\% & \(\pm\)1 \\ Chlorite (Mg,Fe)\({}_{3}\)(Si,Al)\({}_{4}\)O\({}_{10}\) (OH)\({}_{2}\)(Mg,Fe)\({}_{3}\)(OH)\({}_{6}\) & 5\% & 3\% & - & 11\% & 9\% & 6\% & \(\pm\)1 \\ Kaolinite Al\({}_{2}\)Si\({}_{2}\)O\({}_{5}\)(OH)\({}_{4}\) & 7\% & 9\% & - & 9\% & 3\% & - & \(\pm\)1 \\ Smectite +1/S (Na,Ca)\({}_{0.3}\) (Al,Mg)\({}_{2}\)Si\({}_{4}\)O\({}_{10}\)(OH)\({}_{2}\cdot\)n(H\({}_{2}\)O) & - & - & - & 13\% & 7\% & 5\% & \(\pm\)1 \\ Fe oxyhydroxoxides Fe(O,OH,H\({}_{2}\)O) & - & - & - & 5\% & 4\% & 4\% & \(\pm\)1 \\ Accessories & 3\% & 5\% & 1\% & 2\% & 2\% & 2\% & \(\pm\)1 \\ \hline \multicolumn{8}{c}{Particle size} \\ \hline Median (\(\mu\)m) & 250 & 260 & 100 & 2.3 & 2.8 & 1.1 & \(\pm\)1 \\ Sand \textgreater{} 64 \(\mu\)m (\%) & 90 & 80 & 65 & 23 & 10 & 3 & \(\pm\)1 \\ Silt 4-64 \(\mu\)m (\%) & 8 & 13 & 27 & 29 & 47 & 35 & \(\pm\)1 \\ Clay \textless{} 4 \(\mu\)m (\%) & 2 & 7 & 8 & 48 & 43 & 62 & \(\pm\)1 \\ \hline \end{tabular}
\end{table} 
Table 1: Chemical and mineralogical composition, and particle size distribution of the CDR (R1–R2), the sand (C) and the three clays (M-G-S). A laboratory-scale simulation of the industrial manufacturing cycle of clay bricks was carried out through body preparation, shaping, drying, and firing. In particular, the following working phases were carried out:  
1. clay grinding with a jaw crusher (<20 mm) and a hammer mill (<1 mm). The finest fraction i.e., <6 mm, was subsequently ground on a laboratory scale. The different fractions were thus obtained and were mixed, on the basis of their chemical composition and particle size distribution, with the two most representative CDR batches selected (R1 \(\leq\) 0.125 mm and R2 = 0.6-0.125 mm).