## 3 Results and Discussions
### Effect of Nanoparticles on Unconfined Compressive Strength (UCS)  
The variation of the UCS for the untreated and treated soil specimens after one, seven, and 14 days of curing are demonstrated in Figure 4. It is observed that the UCS for the treated soils were significantly greater than that of the untreated soil at the various curing duration. It is also noted that the treated soil samples experienced a gain in strength with increasing curing duration. The improvement in the strength of MS and CS at a shorter curing period is associated with the flocculation/agglomeration of soil particles due to the cation exchange process that led to reduced DDL thickness. The flocculation of soil particles increases the effective grain size, and thus increases the contact between the soil particles, and hence resulted in the enhanced strength of the compacted soil. At a longer curing period, the increase in the UCS can be attributed to the formation of cementing gels, including magnesium silicate hydrate (M-S-H), magnesium aluminate hydrate (M-A-H), calcium silicate hydrate (C-S-H), and calcium aluminate hydrate (C-A-H) due to the nanoparticles-soil interaction, which improved the bonding of the soil particles, and consequently increased the UCS of the treated soil [35]. Likewise, the nanoparticles turn to fill the voids of the soils effectively; hence, decreasing the porosity and increasing the particle-particle contact. Consequently, a further increase in the UCS was observed for the treated specimens. It is also observed that the strength improvement of CS was superior to that of MS samples at various curing durations. This strength variation is associated to the smaller hydrated radius of Ca\({}^{2+}\) compared to Mg\({}^{2+}\) (0.412 nm for Ca\({}^{2+}\) versus 0.428 nm for Mg\({}^{2+}\)) [36], leading to stronger electrostatic attraction between Ca\({}^{2+}\) and the negatively charged clay. It is reported that a smaller hydrated radius will have weaker hydration capability due to its lower affinity to the water molecules; hence, contributing to the higher retention of the Ca\({}^{2+}\) on the clay surface [37]. This phenomenon inevitably triggers the higher rate of formation of cementing gels, particularly C-S-H and C-A-H, causing the superior performance of CS compared to MS. In fact, the UCS of MS (241 kPa) and CS (276 kPa) after 7 days of curing were superior to the UCS reported by [38; 39] that performed investigations on the residual soils treated with (i) potassium hydroxide and untreated coil fibers (170 kPa), (ii) potassium hydroxide and treated coil fibers (230 kPa), and (iii) rice husk ash (150 kPa) at the same curing period.  
Figure 3: Variations of hydraulic conductivity for untreated and nanoparticles-treated soil specimens over permeation time.  
Table 2 summarizes the results of one-way ANOVA for untreated and treated soil specimens based on their respective UCS at different curing periods. As observed from Table 2, the calculated P value 0.00201 is smaller than the significance level of 0.05. This implies that the soil stabilization methods (untreated soil and treated soils with calcium and magnesium hydroxide particles) have significant impact on the mean UCS at different curing periods (one, seven, and 14 days). Since the ANOVA analyses show significant differences due to treatment methods, the mean UCS for untreated and treated soils were further compared by adopting [PERSON]'s least significant difference method, and the results of the analysis are provided in Table 3. It is clearly noticed that the mean difference between treated soils with calcium or magnesium hydroxide nanoparticles and untreated soil are statistically significant at a significance level of 0.05. Hence, it can be concluded that the soil treatment methods using calcium hydroxide and magnesium hydroxide nanoparticles affects the UCS development of soil samples.