# Sustainable Production of Building Blocks by Reusing Stone Waste Sludge
## 3 Results and Discussion
### Inert Two-Component Mixtures
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Specimen** & **PC** & **SWS** & **CS** & **W** & **DW 1** & **MCS 1** & **WS 1** & **h 1** & **Ss 1** \\ \hline  & **[g]** & **[g]** & **[g]** & **[g]** & **[g]** & **[MPa]** & **[g]** & **[cm]** & **[cm2]** \\ \hline A1 & 532.00 & 1684.00 & 1684.00 & 533.91 & 4433.91 & 4.85 & 4006.00 & 7.04 & 5.65 \\ A2 & 532.00 & 1684.00 & 1684.00 & 533.91 & 4433.91 & 4.87 & 3985.00 & 7.05 & 5.65 \\ A3 & 532.00 & 1684.00 & 1684.00 & 533.91 & 4433.91 & 4.85 & 4269.00 & 7.03 & 5.65 \\ \hline \hline \end{tabular}  
* DW = dough weight; MCS = maximum compaction stress; SW = specimen weight; h = specimen height after compaction; Ss = specimen surface area.  
\end{table} 
Table 8: Mixture dosages and compaction tension. During the compaction phase, variations in the applied pressures were necessary. In fact, given the considerable difference in the surface area between the cylindrical specimens and the block (24.79 cm\({}^{2}\) for the cylinders and 300 cm\({}^{2}\) for the block), to exert a surface tension on the block similar to that exerted on the cylinders would have required the application of a remarkably high pressure of about 975.6 kN. We then proceeded with compression by stopping the pressure at 145 kN, a value indicated by Hyperbrick (Table 8). At the end of the compaction process, the specimens were removed from the mold and placed in an accelerated curing chamber at a constant temperature of 70 \({}^{\circ}\)C for 7 days, completely immersed in water. At the end of the curing period, the specimens were taken out (Figure 21), and their density, which was about 1.95 g/cm\({}^{3}\), was calculated, as well as the volume loss due to compaction, which resulted in a reduction in the block height from 10 cm of the formwork to about 7 cm. The blocks were tested for compressive strength according to UNI EN 772-1:2002 (Figure 22), and the results (Table 9) show an average strength of 13.15 MPa, as expected, lower than that recorded for the same mixture placed in cylindrical specimens subjected to higher compaction. The analysis of the failure mechanism of the specimens (Figure 23) showed failure surfaces according to the indirect hyperboloid. In addition, the surface that failed along all four sides of the block had very small thicknesses compared to the surface of the entire specimen, while the core of the specimen remained intact and compact. Figure 21: The blocks after maturation. Figure 20: Rectangular formwork with upper pressing plate. In order to evaluate the mechanical strengths found in relation to the possible uses of the product, we referred to the ASTM-C90 [59] and the current Italian regulations [60]. In relation to the ASTM standard, it can be seen that each of the samples met the specifications for compressive strength (>12.4 MPa). The Italian standards define the minimum values of the characteristic compressive strength of artificial elements for load-bearing masonry (solid or semi-solid elements) for structures in seismic zones as follows:  
Figure 23: Mechanisms of block failure. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Specimen** & **SWS** & **PC** & **W** & **MCS 1** & **h 1** & **Ss 1** & **Rm 1** & **\(\sigma\)1** & **D 1** & **Cv 1** \\ \hline  & **[\%]** & **[\%]** & **[\%]** & **[MPa]** & **[mm]** & **[mm2]** & **[MPa]** & & **[g/cm3]** & **[\%]** \\ \hline A1 & 43.18 & 13.64 & 13.69 & 4.85 & 70.35 & 29880.00 & 13.22 & & 1.91 & 29.93 \\ A2 & 43.18 & 13.64 & 13.69 & 4.87 & 70.50 & 29745.54 & 12.41 & 0.71 & 1.90 & 30.10 \\ A3 & 43.18 & 13.64 & 13.69 & 4.85 & 70.30 & 29880.00 & 13.82 & & 2.03 & 29.98 \\ \hline \hline \end{tabular}  
* MCS = maximum compaction stress; h = specimen height after compaction; Ss = specimen surface area; Rm = average uniaxial compressive strength; \(\sigma\) = standard deviation; D = apparent density; Cv = volume compaction.  
\end{table} 
Table 9: Design parameters and averages of performed test results. Figure 22: The blocks during the compressive strength test.