# Influence of Xanthan Gum-Based Soil Conditioners on the Geotechnical Properties of Soils
## 3 Methods  
The preparation of specimens, the test procedures, and the evaluation of the results followed the standard test methods outlined in Table 3. Most of the investigations were carried out on both the untreated soils and the mixtures; however, that was not feasible in all cases. For example, during the drying of the mixtures, the properties of the SC hydrogel changed notably, and the determination of the plastic limit was not possible. Due to the nature of the SCs (sensitivity to water, swelling, etc. ), the particle density and the particle size distribution of the mixtures were not determined. The water absorption of the untreated soils and the mixtures was determined on crushed dry specimens with particles smaller than 0.355 mm and an initial mass of 1.0 g. At least two test repetitions were conducted for each untreated soil or mixture. Following the recommendation of the standard, the water absorption was assessed after 24 h (w\({}_{\text{A,24h}}\)). The specimens were placed into the oedometer, or direct shear cell, with dry porous plates and submerged under water, allowing them to swell. This enabled the measurement of the compressibility, the shear strength, and the hydraulic conductivity in a saturated state, as well as the swelling of the untreated soils and mixtures. After undergoing swelling at \(\sigma_{v}t=4.5\) kPa in the oedometer, specimens were subjected to incremental loading and unloading in the following load stages: 12.5 kPa, 25 kPa, 50 kPa, \begin{table}
\begin{tabular}{c c c} \hline \hline
**Soil** & **Soil Conditioner** & **Dosage** & **Mixture Label** \\ \hline SC\_R & low, L, 0.4\% & S*+SC\_R L \\ SC\_R & high, H, 1.7\% & S*+SC\_R H \\ SC\_CG & high, H, 1.7\% & S*+SC\_CG H \\ SC\_ZZC & high, H, 1.7\% & S*+SC\_ZZC H \\ \hline \hline \end{tabular} S\({}^{\text{s}}\)—represents the identification number of the soil (SI, S2, S3).  
\end{table} 
Table 2: Investigated mixtures. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & **Standard** & **Device/Method Description** & \
\begin{tabular}{c} **Untreated** \\ **Soil** \\ **Moxtures** \\ \end{tabular} &
\begin{tabular}{c} **Soil** \\ **Moxtures** \\ \end{tabular} \\ \hline Gravimetric water content, w\({}_{0}\) & EN ISO 17892-1 [27] & Dried at 45 \({}^{\circ}\)C & \(\blacktriangledown\) & \(\blacktriangledown\) \\ Particle density, \(\rho_{\text{S}}\) & EN ISO 17892-3 [28] & Pycnometer & \(\blacktriangledown\) & \(\blacktriangledown\) \\ Particle size distribution & EN ISO 17892-4 [29] & Wet and dry sieving, hydrometer & \(\blacktriangledown\) & \(\blacktriangledown\) \\ Water absorption, w\({}_{\text{A,24h}}\) & DIN 18132 [30] & Enslin–Neff/1 g specimen & \(\blacktriangledown\) & \(\blacktriangledown\) \\ Compressibility—oedometer & EN ISO 17892-5 [31] & 70/20 mm fixed ring & \(\blacktriangledown\) & \(\blacktriangledown\) \\  & cell oedometer & & & \\ Shear strength—direct shear test & EN ISO 17892-10 [32] & 60/60/20 mm shear box & \(\blacktriangledown\) & \(\blacktriangledown\) \\ Hydraulic conductivity, k\({}_{\text{10}^{\circ}\text{C}}\) & EN ISO 17892-11 [33] & Falling head, oedometer cell & \(\blacktriangledown\) & \(\blacktriangledown\) \\ Plastic limit, w\({}_{\text{P}}\) & EN ISO 17892-12 [34] & & \(\blacktriangledown\) & \(\blacktriangledown\) \\ Liquid limit, w\({}_{\text{L}}\) & EN ISO 17892-12 [34] & & \(\blacktriangledown\) & \(\blacktriangledown\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: List of laboratory investigations, associated standards, methods, and devices used for investigations, and investigation plan for the untreated soils and the mixtures. 100 kPa, 200 kPa, 100 kPa, 50 kPa, 25 kPa, 4.5 kPa. The saturated hydraulic conductivity was measured using a falling head permeameter at the end of the consolidation in loading stages of 25 kPa and/or 50 kPa. The oedometer tests and measurements of the saturated hydraulic conductivity were performed on two parallel specimens prepared from the same untreated soil or mixture.