# Recycling Construction and Demolition Residues in Clay Bricks
## 3 Results and Discussion
### Technological Behaviour after Firing
** \\ \hline Atterberg plastic limit (PL) & wt\% & 20.3 & 20.3 & 21.2 & 26.9 & 28.2 & 30.1 & 24.2 & 25.5 & 25.8 & \(\pm\)0.1 \\ Atterberg liquid limit (LL) & wt\% & 36.0 & 38.5 & 40.7 & 51.7 & 53.4 & 53.7 & 46.1 & 46.6 & 47.4 & \(\pm\)0.1 \\ Atterberg plastic index (PI) & wt\% & 15.7 & 18.1 & 19.5 & 24.8 & 25.3 & 23.8 & 21.9 & 21.2 & 21.7 & \(\pm\)0.1 \\ Working moisture (WI) & \% & 20.4 & 20.6 & 21.2 & 25.6 & 26.2 & 26.7 & 26.7 & 27.9 & 29.9 & \(\pm\)0.1 \\ Bigot moisture (\(W_{0}\)) & wt\% & 20.4 & 20.6 & 21.2 & 25.6 & 26.2 & 26.7 & 26.7 & 27.9 & 29.9 & \(\pm\)0.1 \\ Weight loss with shrinkage (\(W_{1}\)) & \% & 47.0 & 55.0 & 50.5 & 48.0 & 53.0 & 49.5 & 39.5 & 46.5 & 43.0 & \(\pm\)0.1 \\ Weight loss without shrinkage (\(W_{2}\)) & \% & 53.0 & 45.0 & 49.5 & 52.0 & 47.0 & 50.5 &Analyzing the modulus of rupture, expect to find lower values in samples with CRDs compared to batches containing sand, given the greater porosity and lower density. As observes in Figure 2 an unexpected trend for clays S and G occur. their modulus of rupture is similar, but the bulk density decreases with the increase in flexural strength. \begin{table}
\begin{tabular}{l c c c c c c c c c c c} \hline \hline  & **MC** & **MR1** & **MR2** & **GC** & **GR1** & **GR2** & **SC** & **SR1** & **SR2** & **e.u.** \\ \hline Firing maximum temperature & \({}^{\circ}\)C & 900 & 900 & 900 & 940 & 940 & 940 & 950 & 950 & 950 & - \\ Firing shrinkage (FS) & cm/m & 0.5 & 0.5 & 1.1 & 0.4 & 0.7 & 1.2 & 0.5 & 0.5 & 1.0 & \(\pm\)0.1 \\ Modulus of rupture (MOR-F) & MPa & 11.0 & 10.6 & 8.3 & 14.8 & 15.5 & 15.6 & 16.3 & 18.1 & 18.0 & \(\pm\)0.5 \\ Water absorption (WA) & \%wt & 9.7 & 10.5 & 11.0 & 14.9 & 15.8 & 17.3 & 14.2 & 14.9 & 16.3 & \(\pm\)0.1 \\ Open porosity (OP) & \%vol & 19.3 & 20.6 & 21.4 & 26.6 & 28.1 & 30.2 & 25.8 & 26.7 & 28.5 & \(\pm\)0.2 \\ Bulk density (FBD) & g/cm\({}^{3}\) & 1.992 & 1.957 & 1.942 & 1.780 & 1.786 & 1.746 & 1.815 & 1.792 & 1.746 & \(\pm\)0.01 \\ Normalized strength (MOR-N) & MPa & 13.6 & 13.3 & 10.6 & 20.2 & 21.5 & 22.3 & 22.0 & 24.7 & 25.2 & \(\pm\)1 \\ Brightness (L*) & 1 & 52.97 & 51.27 & 50.34 & 56.31 & 55.98 & 55.22 & 57.08 & 55.86 & 56.47 & \(\pm\)0.5 \\ Red (+) Green (\(-\)) (a*) & 1 & 22.67 & 23.15 & 23.70 & 21.26 & 21.55 & 21.85 & 22.36 & 23.10 & 23.20 & \(\pm\)0.5 \\ Yellow (+) Blue (\(-\)) (b*) & 1 & 26.95 & 26.08 & 27.04 & 26.29 & 27.33 & 27.79 & 27.57 & 28.81 & 29.45 & \(\pm\)0.5 \\ Color difference (\(\Delta\)E*) & 1 & ref & 1.96 & 2.81 & ref & 1.10 & 1.96 & ref & 1.89 & 2.14 & \(\pm\)0.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Firing behavior of batches. Figure 1: Correlation between bulk density versus drying shrinkage of unfired products. \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 Quartz & 28.9 & 35.3 & 33.6 & 30 & 19.9 & 29.4 & 32 & 32 & 19.4 & \(\pm\)0.5 \\ Plagioclase & 4.7 & 9.0 & 5.4 & 39.7 & 24.7 & 33.3 & 34.9 & 36.1 & 22.4 & \(\pm\)0.2 \\ Illite-mica & 4.7 & 5.9 & 3.9 & 6.2 & 4.2 & 7 & 4.2 & 4.8 & 4.0 & \(\pm\)0.2 \\ K-Feldspar & 2.4 & 2.7 & 2.2 & 5.6 & 3 & 5.8 & 4.3 & 7.7 & 2.9 & \(\pm\)0.2 \\ Clinopyroxene & 8.4 & 8.2 & 8.5 & 5.6 & 6.9 & 12.3 & 16.1 & 11.5 & 9.2 & \(\pm\)0.1 \\ Hematite & 2.3 & 3.2 & 3.6 & 3 & 2.3 & 4.1 & 2.7 & 3.5 & 2.2 & \(\pm\)0.1 \\ Amorphous phase & 48.7 & 35.7 & 42.8 & 9.8 & 39 & 8.3 & 5.8 & 4.3 & 39.9 & \(\pm\)1 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Phase composition of fired clay bricks. This behavior was once again linked to differences in mineralogical composition; the residues were richer in the carbonate fraction than sand, which during firing lead to the formation of porosity. In all the samples, there was an absence of or, at least, a poor degree of efflorescence, indicating that the CDRs has no detrimental effect compared to the reference sand.