## 3 Testing Results and Analysis
### Unconfined Compression Test  
After dry cement is mixed with mudstone clods, the hydration of cement produces gels that fill a void. The gel increases the compactness of the clay framework and improves the clods. To understand the effectiveness of the implemented improvements, unconfined compression strength was used as the basic indicator of mudstone that was improved with the addition of cement. Unconfined compression tests were conducted per ASTM D2166. The tested items included specimen preparation methods, clods, number of curing days, cement addition, moisture content, and dry density variables. An explanation and analysis of the treated and untreated soil samples are provided. Figure 7a presents the curves for an untreated specimen clod with grains that passed through #4 sieves, with static methods used to prepare the specimens. Dry density ranged from 17.5 to 20.0 kN/m\({}^{3}\), the unconfined compression strength ranged from to 15.1 kPa, and the corresponding stain ranged from 0.83% to 1.74%. Unconfined compression strength appeared to increase with an increase in dry density. Similar trends were observed for the other two clod grain sizes. Figure 7b presents the treated specimens of various clods with a dry density of 19.5 kN/m\({}^{3}\). Grains that passed through a #4 sieve yielded an unconfined compression strength of 98.0 kPa and a corresponding strain of 1.53%. The unconfined compression strength of grains that passed through or strain was 1.59%. The unconfined compression strength of grains that passed through or were retained on a 3/4\" sieve was 57.0 kPa and the corresponding strain was 1.28%. In summary, the unconfined compression strength was highest for clod grain that passed through the #4 sieve, followed by the #4-3/4\" sieve and >3/4\" sieve. Figure 8a presents the relationship between unconfined compression strength q\({}_{\text{u}}\) and dry density \(\gamma_{\text{d}}\) of mudstone specimen clods. It indicates that the compaction method generated the highest unconfined compression strength, followed by the static and kneading methods. The treated specimens with C = 8% and grains that passed through the #4 and #4-3/4\" sieves after 28 days of curing exhibited higher unconfined compression strength q\({}_{\text{u}}\) relative to the other specimens. In 2021, [PERSON] et al. [26] proposed that the two factors cement and density influence the strength of marine clay that is improved through the use of cement. Figure 8a indicates that the mudstone specimens with six dry density levels yielded unconfined compression strength levels of between 10 and 400 kPa. However, after 8% cement paste was added to the specimens, which were then cured for 28 days, the specimens' unconfined compression strength increased to between 500 and 1200 kPa. Under the research conditions proposed by the present study, the addition of cement paste was more effective than an increase in dry density. Figure 6: Compaction curves and zero air void curves (ZAVC) from the compaction tests for various mix conditions: (**a**) mudstone; (**b**) mudstone-cement. Figure 9a,b presents the relationships between elastic modulus E\({}_{50}\) and dry density \(\gamma_{\rm d}\) in mudstone and mudstone-cement specimens, respectively. The trends presented by the aforementioned figures were identical to those in Figure 8. Among the mudstone specimens with six dry density levels, their elastic modulus E\({}_{50}\) was between 1 and 24 MPa. After the specimens with added cement paste underwent 28 days of curing, their elastic modulus E\({}_{50}\) was between 20 and 120 MPa. The relationships between elastic modulus E\({}_{50}\) and unconfined compression strength q\({}_{\rm u}\) (Figures 8 and 9) are plotted in Figure 10. For the mudstone specimen formula, E\({}_{50}\) = 47.699 q\({}_{\rm u}\) and R\({}^{2}\) = 0.8708, whereas for the mudstone-cement specimen formula, E\({}_{50}\) = 69.397 q\({}_{\rm u}\) and R\({}^{2}\) = 0.9693. In 2017, [PERSON] et al.