## 2 Materials and Methods  
The investigated material comes from a clay pit located in Oasi Lipu in Torrile, Italy. Table 1 lists some properties of the natural soil (TQ0); Table 2 lists its particle sieve fraction. \begin{table}
\begin{tabular}{c c c c c} \hline
**Property** & **Symbol** & **Reference Standard** & **Value** & **Unit** \\ \hline Liquid limit & W\({}_{\text{L}}\) & [26] & 58 & \% \\ Plastic limit & W\({}_{\text{P}}\) & [27] & 26 & \% \\ Plasticity index & P\({}_{\text{I}}\) & [27] & 32 & \% \\ Water content & w & [28] & 27.51 & \% \\ Retirement limit & Retirement limit & [26; 27] & 16.1 & \% \\ Sulphates content & Sulphates & [29] & 0.05 & \% \\ Organic Substance & Organic Substance & [29] & 3.4 & \% \\ Initial consumption of lime & ICL & [19] & 3.0 & \% \\ Methylene Blue & Methylene Blue & [30] & 2.81 & \\ \hline \end{tabular}
\end{table} 
Table 1: TQ0 properties. Table 2 lists the TQ0 particle sieve fraction. Therefore, the chemical and physical characteristics of the natural soil (i.e., Atterberg's limits and percentage passing at 0.002 mm) allow it to be classified as the group index A7-6 according to the standard ASTM D3282-15 [31]. Adding quicklime with different percentages (3%, 4%, 5%, and 6%), the particle size distribution and the Atterberg's limits change: The examined soil can be efficacy-stabilized with quicklime. In order to identify the examined materials, in this study, the treated soils are named TQN, where N is the percentage of added quicklime. Given the obtained Atterberg's limits, not disclosed herein for the sake of brevity, two percentages by mass of quicklime have been considered in this study: 3% and 5%. Regarding TQ0, the first value is ICL; the second value is LSO. Indeed, 5% by mass of quicklime is the highest percentage that improves W\({}_{\text{L}}\), W\({}_{\text{P}}\), and IP over time: 6% of quicklime does not improve the soil parameters compared to 5%. The bearing capacity of the treated soil increases with the percentage of quicklime, and 5% of added quicklime ensures the best mechanical performances. The California bearing ratio (i.e., a penetration test that compares the bearing capacity of the examined material with that of a well-graded crushed stone) [30] is 3% for TQ0, 25% for TQ3, 42% for TQ4, and 58% for TQ5. The opposite trend has been observed for swelling (sw) after 4 d imbibition: sw is 1.3% for TQ0, 0.11% for TQ3, 0.07% for TQ4, and 0.017% for TQ5. According to the modified Proctor test [32], Figure 1 shows the relationship between the achievable dry bulk density and the moisture content (w). The added lime results in flatter compaction curves: The optimum moisture content increases with the stabilizer content and the maximum dry density decreases as the percentage of lime increases: This result complies with the expected effects of the stabilization treatment. Indeed, lime stabilization of fine-grained soils results in a load-bearing capacity increase and swelling and shrinkage potential decrease [33]. Therefore, a stabilized soil has higher strength, lower permeability, and lower compressibility than the native soil. TQ0, TQ3, and TQ5 samples have been analyzed. Before the XRD tests [34], the specimens have been dried in an oven at 40 \({}^{\circ}\)C for 72 h in order to minimize the sensibility of clayy non-treated minerals to strong temperature ranges that change the properties of clay [35]. However, not all sources in the literature declare the need for drying the treated specimens in an oven at 40 \({}^{\circ}\)C for 72 h. At this purpose, the authors compared diffractograms of TQ3 before and after drying in order to verify the effect of moisture on the XRD results: No significant differences in terms of peak intensity and position have been found. The only detectable difference concerns a greater definition of the peaks, which are more detectable from the background noise. However, it has a very slight diversity: For this reason, diffraction patterns of samples stove-dried at 40 \({}^{\circ}\)C will be referenced.