# Recycling Construction and Demolition Residues in Clay Bricks
## 3 Results and Discussion
### Technological Behaviour after Firing  
Tables 4 and 5 present the results related to the firing behavior of ceramics batches. In all the products, the introduction of CDR fractions leads to an increase in both water absorption and firing shrinkage. Taking into account the flexural strength of the firing products, a decrease of MOR in the CDR products would be expected given the greater porosity extent and lower density appearing. \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline
**Weight (\%)** & **MC** & **MR1** & **MR2** & **GC** & **GR1** & **GR2** & **SC** & **SR1** & **SR2** & **e.u.** \\ \hline Clay M & 85 & 85 & 85 & 85 & 85 & 85 & 85 & 85 & 85 & 85 & \(\pm\)0.3 \\ Clay G & - & - & - & - & - & - & - & - & - & \(\pm\)0.3 \\ Clay S & - & - & - & - & - & - & - & - & - & \(\pm\)0.3 \\ Sand C & 15 & - & - & 15 & - & - & 15 & - & - & \(\pm\)0.3 \\ CDR R1 & - & 15 & - & - & 15 & - & - & 15 & - & \(\pm\)0.3 \\ CDR R2 & - & - & 15 & - & - & 15 & - & - & 15 & \(\pm\)0.3 \\ \hline \multicolumn{8}{c}{Chemical composition} \\ \hline SiO\({}_{2}\) & 65.62 & 62.21 & 59.72 & 64.28 & 60.87 & 58.38 & 62.21 & 58.80 & 56.31 & \(\pm\)0.35 \\ TiO2 & 0.67 & 0.72 & 0.73 & 0.67 & 0.72 & 0.73 & 0.72 & 0.77 & 0.77 & \(\pm\)0.01 \\ Al\({}_{2}\)O\({}_{5}\) & 17.43 & 18.00 & 17.75 & 14.10 & 14.66 & 14.42 & 15.16 & 15.72 & 15.47 & \(\pm\)0.15 \\ F\({}_{\rm Fe2}\)O\({}_{3}\) & 6.54 & 6.98 & 7.08 & 5.14 & 5.59 & 5.69 & 5.76 & 6.21 & 6.31 & \(\pm\)0.07 \\ MnO & - & 0.01 & 0.01 & 0.12 & 0.13 & 0.13 & 0.11 & 0.12 & 0.12 & \(\pm\)0.01 \\ MgO & 2.84 & 3.60 & 4.08 & 2.72 & 3.47 & 3.96 & 4.08 & 4.84 & 5.33 & \(\pm\)0.02 \\ CaO & 3.39 & 5.09 & 7.43 & 8.45 & 10.15 & 12.50 & 7.25 & 8.95 & 11.29 & \(\pm\)0.01 \\ Na\({}_{2}\)O & 1.02 & 1.02 & 0.92 & 1.48 & 1.48 & 1.39 & 1.33 & 1.33 & 1.23 & \(\pm\)0.01 \\ K\({}_{2}\)O & 2.50 & 2.35 & 2.25 & 2.91 & 2.77 & 2.67 & 3.25 & 3.10 & 3.00 & \(\pm\)0.01 \\ P\({}_{2}\)O\({}_{5}\) & - & 0.03 & 0.02 & 0.13 & 0.15 & 0.15 & 0.14 & 0.17 & 0.16 & \(\pm\)0.01 \\ \hline \multicolumn{8}{c}{Mineralogical composition} \\ \hline Quartz SiO\({}_{2}\) & 32 & 27 & 26 & 33 & 28 & 26 & 36 & 32 & 30 & \(\pm\)1 \\ Plagioclase (Na\({}_{4}\)Ca)(Si,Al)\({}_{4}\)O\({}_{8}\) & 6 & 5 & 4 & 10 & 10 & 9 & 11 & 10 & 10 & \(\pm\)1 \\ Orthoclase KAlSi\({}_{3}\)O\({}_{8}\) & 3 & 1 & 1 & 3 & 1 & 1 & 3 & 1 & 1 & \(\pm\)1 \\ Calcite CaCO\({}_{3}\) & 6 & 7 & 9 & 13 & 15 & 17 & 5 & 6 & 8 & \(\pm\)1 \\ Dolomite CaMg(CO\({}_{3}\))\({}_{2}\) & - & 2 & 4 & 0 & 2 & 4 & 9 & 10 & 12 & \(\pm\)1 \\ Illite-mica K(Al,Mg,Fe)\({}_{2}\) (Si,Al)\({}_{4}\)O\({}_{10}\)(OH)\({}_{2}\)(H\({}_{2}\)O) & 20 & 21 & 20 & 21 & 20 & 22 & 24 & 23 & \(\pm\)1 \\ Chlorite (Mg,Fe)\({}_{3}\)(Si,Al)\({}_{4}\)O\({}_{10}\)(OH)\({}_{2}\)(Mg,Fe)\({}_{3}\)(OH)\({}_{6}\) & 9 & 10 & 10 & 8 & 8 & 8 & 5 & 6 & 6 & \(\pm\)1 \\ Kaolinite Al\({}_{2}\)Si\({}_{2}\)O\({}_{5}\)(OH)\({}_{4}\) & 8 & 9 & 9 & 3 & 4 & 4 & - & 1 & 1 & \(\pm\)1 \\ Smectite + I/S (Na,Ca)\({}_{0,3}\) & 11 & 11 & 11 & 6 & 6 & 6 & 4 & 4 & 4 & \(\pm\)1 \\ (Al,Mg)\({}_{2}\)Si\({}_{4}\)O\({}_{10}\)(OH)\({}_{2}\):n(H\({}_{2}\)O) & & & & & & & & & & \\ Fe oxyhydroxes Fe(O,OH,H\({}_{2}\)O) & 4 & 4 & 4 & 3 & 3 & 3 & 3 & 3 & 3 & \(\pm\)1 \\ Accessories & 2 & 2 & 2 & 2 & 2 & 2 & 2 & 2 & 2 & \(\pm\)1 \\ \hline \multicolumn{8}{c}{Particle size distribution} \\ \hline Median (\(\mu\)m) & 17 & 39 & 41 & 17 & 40 & 41 & 16 & 38 & 40 & \(\pm\)0.5 \\ Sand \textgreater{}64 \(\mu\)m (\%) & 29 & 33 & 32 & 18 & 22 & 21 & 12 & 16 & 15 & \(\pm\)0.5 \\ Silt \textless{}4–64 \(\mu\)m (\%) & 29 & 26 & 27 & 44 & 41 & 42 & 34 & 31 & 32 & \(\pm\)0.5 \\ Clay \textless{}4 \(\mu\)m (\%) & 42 & 41 & 42 & 38 & 37 & 38 & 54 & 53 & 54 & \(\pm\)0.5 \\ \hline \multicolumn{8}{c}{e.u. = experimental uncertainty.} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Formulation, chemical and mineralogical composition, and particle size distribution of the batches. \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline
**Parameter** & **Unit** & **MC** & **MR1** & **MR2** & **GC** & **GR1** & **GR2** & **SC** & **SR1** & **SR2** & **e.u.