## 3 Experimental Work
### Soil Characterization  
To examine the engineering characteristics and mineralogical phases of the soil specimens from the Najran area (Figure 2), primary characterization studies were carried out in accordance with ASTM standards. Specific gravity, Arterberg limits, and grain size distribution were used to classify the soil during the preliminary studies. The mineralogical composition of the soil was further assessed using XRD (X-ray diffraction) and SEM (scanning electron microscopy). According to [30], the specific gravity was calculated. A pair of \"disturbed\" specimens were used in the experiment and each specimen was put through ASTM sieve No. 4 before being used. The specific gravity was calculated using the average of both specimens. On specimens passing ASTM sieve No. 40, liquid and plastic limits were evaluated using [31]. All soil specimens were subjected to the [32] grain size distribution test.  
\begin{table}
\begin{tabular}{c c} \hline
**Element** & **Composition Range (\%)** \\ \hline SiO2 & 45–77 \\ \hline Al\({}_{2}\)O\({}_{3}\) & 15–20 \\ \hline CaO & 3–15 \\ \hline Fe\({}_{2}\)O\({}_{3}\) & 6–16 \\ \hline K\({}_{2}\)O & 3–5 \\ \hline MgO & 1–4 \\ \hline Na\({}_{2}\)O & 0–3 \\ \hline P\({}_{2}\)O\({}_{3}\) & 0–0.04 \\ \hline TiO\({}_{2}\) & 0–2.33 \\ \hline \end{tabular}
\end{table}
Table 1: Chemical composition of CACW.  
According to [25], a material's mineralogical distribution can be used to anticipate how it will behave and react in different situations. The mineralogical investigation employed only ten grams of the examined soil. The mineralogical compositions of the soil specimens were determined using SEM with Field- Electron (Tescan Lyra-3) and Powder X-ray Diffraction techniques (Ultima IV). The secondary electron mode was used for SEM. Before the experiments, the samples were covered with gold (Au) to boost their conductivity. In addition, the elemental compositions of the soil were measured using a dispersive energy X-ray (EDX) test and a scanning electron microscope (SEM) for all samples. Scanning electron microscopy (SEM) can be used to analyze the microstructural characteristics and the elemental composition of the carbonate samples, according to [28].  
Soil specimens were ground into a powder using an agate mortar pestle for XRD examination. The specimens were then compressed into sample holders and inserted into the apparatus for examination. The powder method of X-ray diffraction is utilized, and the Powder XRD Ultima IV is the brand and model of the equipment used.  
The sample's crystals are organized in an arbitrary manner. A monochromatic (of a single wavelength) X-ray beam strikes a crystal. X-rays that hit the parallel surfaces that make up the crystal will reflect at an angle because of this, as shown by Miller indices (jkl). A series of reflections can be seen, depending on the type of minerals in the soil. The crystals in the sample are arranged in a random pattern. By comparing the intensity and angle of incidence with those of standard minerals, it is possible to determine the type and number of minerals present in the sample. The diffraction pattern is contrasted with normative diffraction patterns created by the Joint Committee of Powder Diffraction Standards (JCPDS) for various stages.