## 2 Materials and Methods  
The fly ash sample was collected from a local Georgia power plant for this study. The plant is a one of the largest generating facilities in the nation and is continually rated among the top generating fossil-fueled sites in the nation. The plant usually burns 1100 tons of coal an hour, the equivalent of three 95-car trainloads a day [10]. The fly ash sample used in this study was Class F; it was dark gray in color (Figure 1a). Although Class C fly ash was not used in this study, the physical appearance of both Class F and Class C fly ash are shown in Figure 1a,b. The range of element oxides present in \"Class F\" and \"Class C\" fly ash as reported in various literature is discussed and consolidated by [PERSON] and [PERSON] [11] and is listed in Table 1. The soil samples used in this study were collected from a local construction site in Cobb County in accordance with the ASTM specifications (ASTM D420-98). The visual classification of the soil sample was reddish brown in color (Figure 1c) and well graded. The soil sample was prepared for testing by air-drying for 24 h before any test was conducted. Four set of experiments (soil and soil-fly ash mix) were run to accomplish the objectives of this study. The flowchart in Figure 2 shows the experimental set up with other relevant information. The percentages of fly ash (0%, 40%, 50%, and 60%) in the soil-fly ash mixtures and the curing periods (0, 2, 8, and 28 days) were arbitrarily selected for the experiments. Higher percentages of fly ash were selected to find the highest optimum fly ash content to maximize the beneficial use because most of the studies conducted used a fly ash content of 20% as the highest, except for one where the maximum fly ash content used was 40%. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Element**} & \multirow{2}{*}{**Oxide**} & \multicolumn{2}{c}{**Concentration (\%)**} \\ \cline{3-4}  & & **Class C** & **Class F** \\ \hline Calcium (Ca) & CaO & 15.1–54.8 & 0.50–14.0 \\ Silicon (Si) & SiO\({}_{2}\) & 11.8–46.4 & 37.0–62.1 \\ Aluminum (Al) & Al\({}_{2}\)O\({}_{3}\) & 2.6–20.5 & 16.6–35.6 \\ Iron (Fe) & Fe\({}_{2}\)O\({}_{3}\) & 1.4–15.6 & 2.6–21.2 \\ Magnesium (Mg) & MgO & 0.1–6.7 & 0.3–5.2 \\ Potassium (K) & K\({}_{2}\)O & 0.3–9.3 & 0.1–4.1 \\ Sodium (Na) & Na\({}_{2}\)O & 0.2–2.8 & 0.1–3.6 \\ Sulfur (S) & SO\({}_{3}\) & 1.4–12.9 & 0.02–4.7 \\ Phosphorus (P) & P\({}_{2}\)O\({}_{5}\) & 0.2–0.4 & 0.1–1.7 \\ Carbon (C) & TiO\({}_{2}\) & 0.6–1.0 & 0.5–2.6 \\ Manganese (Mn) & MnO & 0.03–0.2 & 0.03–0.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Percent range of element oxides present in “Class C” and “Class F” fly ash. Figure 1: Appearance of typical (**a**) Class F fly ash and (**b**) Class C fly ash and (**c**) soil used in this study. Two methods were used to experimentally determine the specific gravity of the soil. One was performed by a water pycnometer (ASTM D854) and the other by the gas pycnometer technique (ASTM D5550). Mechanical sieving was used for the coarse-grained portion and hydrometer analysis was used for the fine-grained portion of the material for grain size distribution, in accordance with ASTM D2487-06, ASTM D422, D1140 and AASHTO T88 and ASTM D7928-17. The grain size distribution curve for the soil used in this study is presented in Figure 3.  
assess the magnitude and rate of volume change of the soil sample and the soil-fly ash mixtures that were restrained laterally and loaded and drained axially. Both the UCS and consolidation tests were performed using the OMC obtained from the ASTM D698 experiments. The obtained data from the consolidation test were used to determine the compression and swelling indices. Duplicate or triplicate runs of the experiments, as needed, were performed and the averages of the values falling within 10% of the individual values were reported. Detailed procedures and data can be found in [PERSON] (2018). A study conducted by [PERSON] et al. [PERSON] et al.