## 3 Results and Discussion
### Bricks  
The results of linear shrinkage, water absorption, and colorimetry of brick samples produced using 10%, 50%, and 100% of waste sand are reported in Table 5 and compared to the standard formulation STD. The post-firing linear shrinkage (LS%) shows a slight  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Porcelain Stoneware** & **LS\%** & **St.Dev** & **WA\%** & **St.Dev** & \(\Delta\)E \\ \hline STD & 4.8 & 0.3 & 0.009 & 0.004 & 0 \\ \hline SF10 & 4.7 & 0.1 & 0.0015 & 0.0002 & 0 \\ \hline SF50 & 4.9 & 0.2 & 0.022 & 0.003 & 1 \\ \hline SF100 & 4.3 & 0.1 & 0.02 & 0.01 & 1.73 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Results of linear shrinkage (LS%), water absorption (AA%), and colorimetry (\(\Delta\)E) with standard deviation (St.Dev) of porcelain stoneware samples.  
Figure 3: X-ray diffraction of samples SF100 and STD (Q = Quartz, Mi = Microcline intermediate, M = Mullite, A = Albite).  
increase by adding the foundry sand. The presence of Fe in the foundry sand can influence this behavior.  
The water absorption values for brick samples increase with the amount of foundry sand added. The higher value of WA% was shown by sample F.100 with 12.7 WA%, compared to 8.65 WA% shown by the standard formulation with basalt. This means that, despite the addition of foundry sand, brick samples remain a highly porous material [16].  
For colorimetry measures, the \(\Delta\)E values of samples depend on the amount of sand added. The \(\Delta\)E measures are in the range of 2-3 for all samples compared to the standard formulation, so it can be deduced that there is a distinguishable color variation.  
In Figure 4, the diffractograms obtained for the brick formulations are reported. Even in this case, there are no particular differences between the diffractograms of F.100 and FSTD samples, which show peaks of the same crystalline phases (quartz, hematite, and albite), with a negligible variation in their intensity, due to the variation in the percentage of foundry sand added.  
From the analyses carried out, it is possible to conclude that the introduction of foundry sand as a secondary raw material for tiles and bricks in place of virgin sand modifies the physical properties of the standard samples in an acceptable way. The results obtained using waste foundry sands for ceramic materials may be considered acceptable, compared to similar studies with waste materials found in the literature for tiles and porcelain stoneware, e.g., in terms of water absorption and shrinkage [17; 18] and for bricks [19], on the application which they are intended.  
Figure 4: X-ray diffraction of F.100 and FSTD (Q = Quartz, H = Hematite, A = Albite).  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Brick Sample** & **LS\%** & **St.Dev** & **WA\%** & **St.Dev** & \(\Delta\)E \\ \hline FSTD & 5.2 & 0.9 & 8.6 & 0.4 & 0 \\ \hline F.10 & 6.6 & 0.8 & 10.8 & 0.41 & 1.49 \\ \hline F.50 & 6 & 1 & 12.1 & 0.5 & 1.15 \\ \hline F.100 & 6 & 1 & 12.7 & 0.7 & 2.84 \\ \hline \end{tabular}
\end{table}
Table 5: Results of linear shrinkage (LS%), water absorption (AA%), and colorimetry (\(\Delta\)E) with standard deviation (St.Dev) of brick samples.