# Prediction of Unconfined Compressive Strength in Cement-Treated Soils: A Machine Learning Approach
## 2 Materials and Methods
### Experimental Program  
#### 2.2.1 Sample Preparation  
The soil specimens were prepared by oven-drying at a temperature of 105 \({}^{\circ}\)C, and subsequently milled and sieved. Using the dry unit weight (\(\gamma_{d}\)) of 15.37 kN/m\({}^{3}\) and optimum moisture content (OMC) of 14.9%, the samples were mixed thoroughly in airtight  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**CaO** & **SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **MgO** & **Na\({}_{2}\)O** & **K\({}_{2}\)O** & **SO\({}_{3}\)** \\ \hline
56.2 & 19.8 & 7.1 & 3.6 & 1.2 & 0.38 & 0.69 & 2.9 \\ \hline \end{tabular}
\end{table}
Table 1: Chemical composition (%) of Portland cement type CEM II/B-M(S-LL) 42.5 R.  
plastic bags to prevent moisture loss and to ensure proper hydration and bonding of the cement with the soil particles (Figure 1a).  
The soil-cement mixtures were prepared using four different cement dosages (2.5%, 5%, 7.5%, and 10% by dry weight of soil). These mixtures were placed in stainless steel containers and compacted using a static compaction technique to form cylindrical samples (Figure 1c) for UCS testing. A controlled axial load was applied with a triaxial load frame to achieve the target density (Figure 1b). All samples were molded to a standard size of 3.8 cm in diameter and 7.6 cm in height. The cemented samples were compacted at three different velocities (0.75 mm/min, 1.0 mm/min, and 1.25 mm/min), while the non-cemented control samples were compacted at four velocities (0.5 mm/min, 0.75 mm/min, 1.0 mm/min, and 1.25 mm/min). Each molded sample was carefully extruded after compaction.  
For cement-treated samples, a minimum of 9 specimens were prepared for each combination of cement content and curing period, with 3 replications for each compaction velocity. This resulted in at least 36 specimens for each cement percentage (across four curing periods), yielding a total of 171 cement-treated samples. Additionally, 14 samples without cement were prepared (at least 3 for each compaction velocity). The soil-cement samples were cured for periods of 1 day, 7 days, 14 days, and 28 days at a constant temperature of approximately 23 \({}^{\circ}\)C in a desiccator (Figure 1d). The detailed breakdown of sample configurations is presented in Table 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample** **Preparations**} & \multirow{2}{*}{**Compaction** **Velocities (mm/min)**} & \multicolumn{4}{c}{**Cement Percentages (\%)**} \\ \cline{3-6}  & & **2.5** & **5** & **7.5** & **10** \\ \hline \multirow{3}{*}{For 24 h} & 1.25 & 3 & 4 & 3 & 3 \\  & 1.0 & 3 & 3 & 4 & 4 \\  & 0.75 & 3 & 3 & 3 & 4 \\ \hline \multirow{3}{*}{For 7 days} & 1.25 & 4 & 4 & 4 & 4 \\  & 1.0 & 4 & 4 & 4 & 4 \\ \hline \multirow{3}{*}{For 14 days} & 1.25 & 3 & 4 & 3 & 4 \\  & 1.0 & 4 & 4 & 4 & 4 \\ \cline{1-1}  & 0.75 & 3 & 3 & 4 & 3 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Cement-soil mix samples prepared by static compaction for experimentation.  
Figure 1: Sample preparation: (**a**) Soil mixture in plastic bags. (**b**) Triaxial load frame Tritech (model 28-WF4005, Controls S.p.A., Milan, Italy) used to compact the soil. (**c**) Cylindrical samples. (**d**) Curing in desiccator.