## 3 Results
### SEM-EDS Analyses  
The results of SEM-EDS analyses permit images of samples in grayscale (Figures 11 and 12) and quantitative microanalyses (Figures 13-15) to be obtained. Figure 11a,d show SEM images of TQ0 at 500X and 1000X magnification, respectively; Figure 11b,e show SEM images of TQ3 at 500X and 1000X magnification after a 28 d allowing period, respectively; Figure 11c,f show SEM images of TQ5 at 500X and 1000X magnification, after a 28 d m Figures 13-15 show the EDS spectra of TQ0, TQ3, and T5 at 28 d, respectively. The peak without chemical element in Figure 13 is attributable to iron (7 keV). Figure 12: TQ5 at 28 d mellowing period—1000X. Figure 13: EDS spectrum of TQ0. The comparison between spectra in Figures 13 and 14 highlights the reduction of peaks attributable to the clayey fraction (i.e., Al, Si, K). It confirms the diffraction peak intensity reduction observed at 20 = 26.7273\({}^{\circ}\). The comparison between spectra in Figures 13 and 14 highlights the percentage variation of the chemical elements and confirms the trend due to stabilization observed in Figure 14. Table 4 lists the microanalysis results for TQ0, TQ3, and TQ5 at the 28 d mellowing period. Figure 14: EDS spectrum of TQ3 at 28 d.  
Figure 15: EDS spectrum of TQ5 at 28 d.  
In all the samples, there is a big presence of silicon and calcium, the first due to the clay matrix and quartz contained in the natural soil. In addition, Al, Mg, and K can be related to the clayey matrix. After the 28 d mellowing period, significant quantity changes have happened and the reduction trend of the chemical elements addressable to the clay sample fraction (i.e., Al, Si, and K) is evident (Table 4). These results comply with the XRD analyses (i.e., the reduction of the diffraction peak at 20 = 26.7273\({}^{\circ}\) related to the mineral phases of I and Q). Moreover, a progressive increase in calcium is also clear. In TQ0, a massive calcium presence was found (35.99%), due to the natural composition of the specimen, while its increase in TQ3 and TQ5 (46.38% and 50.52%, respectively) is imputed to the added lime. Finally, the authors carried out experimental SEM-EDS tests on different samples varying the percentage of the added CaO. After a 24 h mellowing period, seven soils (i.e., TQ0, TQ1, TQ2, TQ3, TQ5, TQ6.5, and TQ) were investigated with 16 specimens each. In order to prepare specimens of treated soil, 40 g of TQ0 was taken and dried in an oven at 40 \({}^{\circ}\)C for 72 h to eliminate the moisture in the natural soil (and to avoid damage to the EDS objective lens in the sample chamber). After addition of N by mass percentage of CaO, the treated soil mellowed during 24 h before EDS analysis. The adopted test conditions for SEM-EDS analyses were: Excitation voltage of the tungsten equal to 25 kV; working distance equal to 35 mm; magnification: 100X. From each specimen, five measures of Ca (and other chemical elements) content were obtained. The obtained results were filtered by box plot analysis according to the following procedures:  
* division of observations into quartiles;
* identification and deletion of outlier values (more than 3/2 times of upper quartile or less than 3/2 times of lower quartiles);
* identification of the superior and inferior adjacent values (i.e., greatest and lowest values excluding outliers, respectively);
* calculation of the average using admissible values. Figure 16 shows the average values of the after-treatment Ca content vs. the added quicklime percentages; the regression linear curve has a coefficient of determination equal to 0.9841. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Element** & **Presence in TQ0 (\%)** & **Presence in TQ3 (\%)** & **Presence in TQ5 (\%)** \\ \hline Mg & 0.83 & 1.36 & 0.51 \\ Al & 10.08 & 8.91 & 7.43 \\ Si & 37.00 & 29.69 & 28.97 \\ K & 5.04 & 4.13 & 3.84 \\ Ca & 35.99 & 46.38 & 50.52 \\ Fe & 11.06 & 9.54 & 8.77 \\ Total & 100.00 & 100.00 & 100.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: TQ0, TQ3, and TQ5 28 d microanalysis.