# Sustainable Production of Building Blocks by Reusing Stone Waste Sludge
## 3 Results and Discussion  
### Inert Three-Component Mixtures  
Table 6 shows the test results of the compressive strength and water absorption tests. It shows that the composites had an average density of 2.13 g/cm\({}^{3}\), an average Young's modulus of 1.48 GPa, and a water absorption rate of 10.05%. Figure 11: Flow chart of the production process with raw material identification. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Specimen** & **PC** & **SWS** & **CS** & **W** & **DW 1** & **WS 1** & **h 1** & **d 1** \\ \hline  & **[g]** & **[g]** & **[g]** & **[g]** & **[g]** & **[g]** & **[cm]** & **[cm]** \\ \hline
13.64C80(5/5)13.69 & 48.42 & 153.29 & 153.29 & 48.60 & 403.60 & 386.80 & 7.23 & 5.65 \\
12.00 C80(5/5)13.69 & 42.60 & 156.20 & 156.20 & 48.60 & 403.60 & 394.23 & 7.28 & 5.65 \\
10.00 C80(5/5)13.69 & 35.50 & 159.75 & 159.75 & 48.60 & 403.60 & 387.28 & 7.15 & 5.65 \\
8.30 C80(5/5)13.69 & 29.46 & 162.77 & 162.77 & 48.60 & 403.60 & 392.15 & 7.29 & 5.65 \\ \hline \hline \end{tabular}  
* DW = dough weight; SW = specimen weight; h = specimen height; d = specimen diameter.  
\end{table} 
Table 5: Dosages of doughs containing different percentages of PC. Figure 12 shows how the strengths vary as the amount of water added to the mix changes, and specifically how the strength values, which are all very high, increase as the percentage of water present decreases. In particular (Figure 13), it is interesting to see how a decrease in water ranging from 13% to 12.38% (relative decrease of 0.62%) resulted in a notable increase in the compressive strength from 26.12 MPa to 29.57 MPa (relative increase of 11.67%), while for a subsequent decrease that changes the percentage of water from 12.38% to 10.78% (relative decrease of 1.6%), the increase in compressive strength is much lower in percentage terms, going from 29.57 MPa to 29.92 MPa (relative increase of 1.17%), which suggests a stabilization of the value, making further decreases in water, which would be detrimental to the workability of the mix, insignificant in terms of improving the compressive strength. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Specimen** & **PC** & **W** & **MCS 1** & **AR1** & **Rm 1** & \(\sigma\)1 & **Ym 1** & **D 1** & \(\sigma\)1 & **Wa** & \(\sigma\)1 \\ \hline  & [\%] & [\%] & [MPa] & & & [MPa] & & [GPa] & [g/cm3] & & **[\%]** & \\ \hline
15.79C42.93(3/2/5)13.00 & 15.79 & 13.00 & 42.93 & 0.85 & 26.12 & 1.10 & 1.27 & 2.02 & 0.10 & & \\
15.79C42.93(3/2/5)12.38 & 15.79 & 12.38 & 42.93 & 0.86 & 29.57 & 1.22 & 1.59 & 2.21 & 0.11 & 10.5 & 0.95 \\
15.79C43.04(3/2/5)10.78 & 15.79 & 10.78 & 43.04 & 0.85 & 29.92 & 1.15 & 1.59 & 2.17 & 0.12 & & \\ \hline \end{tabular}  
* MCS = maximum compaction stress; AR = aspect ratio; Rm = average uniaxial compressive strength; YM = average Young’s modulus; D = apparent density; Wa = water absorption; \(\sigma\) = standard deviation.  
\end{table} 
Table 6: Inert Three-Component Mixtures. Design parameters and averages of performed test results. Figure 12: Variation in mechanical strength for the same amount of cement and as the percentage of water changes. The analysis of the stress-strain curves (Figure 14) shows that all the compounds underwent a significant amount of deformation prior to failure. The mix with a higher water content underwent additional compaction, which was quite significant, before it began to resist compressive stresses. This behavior can be attributed to an additional step of expulsion of the free water still present in the mix that is not required for the stechiometric reaction of the cement (the water required for the stoichiometric reaction is equal to 25% of the cement weight). Figure 14: Stress–strain curves for the three different doughs tested. Figure 13: Change in compressive strength in relation to percentage of water present. Based on the compressive strength and density values, a comparison was made with the classification of concretes from UNI EN 206:2021 [57] and NTC 2018 [58].