## 3 Results
### Semi-Industrial Experimentation  
Satisfactory laboratory scale and leaching tests permitted to hypothesize the obtainment of ceramic materials suitable as floor or wall tiles. These products reached good features at temperatures (900-1000 \({}^{\circ}\)C) with 60 min of isotherm time, surely energy-saving  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameters/Anions/** & & & & **Italian Regulation Limit for Inert** \\
**Elements** & & & & **Landfill Disposal** \\  & & & & **D.m.27/9/2010** \\ \hline
**pH a 20 \({}^{\circ}\)C** & 8.63 & 9.82 & 9.91 & 5.5–12.0 \\
**Specific conductivity** (\(\mu\)S/cm) & 145 & 62.0 & 65.4 & - \\
**Nitrate (mg/L)** & \textless{}0.02 & \textless{}0.02 & \textless{}0.02 & 50 \\
**Sulphate (mg/L)** & 15.8 & 2.0 & 2.7 & 100 \\
**Chloride (mg/L)** & 8.45 & 0.27 & 0.43 & 80 \\
**Fluorine (mg/L)** & 1.17 & 0.035 & 0.012 & 1 \\
**Cr total (\(\mu\)g/L)** & 18.5 & 11.4 & 6.30 & 50 \\
**Cd (\(\mu\)g/L)** & \textless{}1 & \textless{}1 & \textless{}1 & 4 \\
**Cu (\(\mu\)g/L)** & 37.9 & 2.10 & 3.33 & 20 \\
**Pb (\(\mu\)g/L)** & 184.8 & 3.80 & 1.20 & 50 \\
**Al (mg/L)** & 0.50 & 0.50 & 0.60 & - \\
**As (mg/L)** & \textless{}0.05 & \textless{}0.05 & \textless{}0.05 & 0.05 \\
**Ba (mg/L)** & \textless{}1 & \textless{}1 & \textless{}1 & 2 \\
**Co (mg/L)** & \textless{}0.02 & \textless{}0.02 & \textless{}0.02 & 0.25 \\
**Fe (mg/L)** & \textless{}0.02 & \textless{}0.02 & \textless{}0.02 & - \\
**Mn (mg/L)** & \textless{}0.02 & \textless{}0.02 & \textless{}0.02 & - \\
**Zn (mg/L)** & 0.50 & \textless{}0.50 & \textless{}0.50 & 0.40 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Leaching test for glazing sludge and the V125 and V75 sintered samples compared to the Italian regulation limits.  
conditions with respect to commercial products (1100-1250 \({}^{\circ}\)C) and furthermore, using alternative raw materials saving the natural resources.  
Samples of V75 composition were undergone by three traditional industrial cycles (described above). The sintering degree on the fired pieces was checked by the determination of W.A.%, L.S%, Apparent Density and Young's modulus (E). Flexural Strength calculated by Equation (4) completes the characterization. The experimental data reported in Table 5 were left as an interval between the lowest and the highest value obtained in order to compare them with the typical data of commercial products.  
From Table 5 it is possible to note that the optimum temperature range is around 1020-1090 \({}^{\circ}\)C. In particular, regarding water absorption at 1087 \({}^{\circ}\)C, the low values permit to classify these materials into Bla Group according to ISO 13006 rule (Bla W.A% \(\leq\) 0.5%). The properties achieved by these samples are compared to those corresponding to commercial porcelain stoneware products (firing at 1200-1250 \({}^{\circ}\)C). The cycle (1020 \({}^{\circ}\)C, 54 min.) could be the most appropriate with a L5% value similar to the commercial products. Regarding water absorption the data are high respect to commercial tiles but it is important to note that all the determinations were conducted on the unglazed materials (support) as a monolithic similar to technical porcelain stoneware or clinker. Surely, glazed products obtained by the cycle at 1020 \({}^{\circ}\)C could reach good values of water absorption, too. Mechanical properties obtained are higher than those relative to commercial tiles used as covering for floors and walls (see Table 5).  
In the case to use the products without glazing, the cycle at 1087 \({}^{\circ}\)C produced specimens with lowest W.A% but higher L.S.% values, this fact can cause calibration problems after firing. In order to optimize the linear shrinkage, future developments of the research have scheduled the reformulation of the mixture introducing a reducing plasticity material (for example rice husk ash).