## 3 Results and Discussion
### Microstructural Analysis  
A series of micrograph study was conducted on three different specimens which were untreated soil (C), stabilized soil mixture with lime (CLF) and stabilized soil mixture with alkaline activation (AA) after 28 days of curing by using the field emission scanning electron microscope. It is clearly seen from Figure 6a that, the untreated clay soil shows a discontinuous and fractured structure with a presence of voids and macropores. At this view, it can be observed that there is high porosity qualified  
Figure 5: Load versus displacement (indirect tensile strength) for (**a**) 7 days, (**b**) 28 days, and (**c**) 90 days. as inter- agglomerate between the clay particles. As the specimen was being zoomed, it can clearly be seen that the clay particles have huge large coated aggregated soil particles among it (Figure 6b). Figure 7 shows the FESEM images for the stabilized soil with lime inclusion fibre, after 28 days curing period. The treated soil matrix with lime (Figure 7) depicts the pozzolanic reaction that occurs to produce cementitious products resulting in compacted soil particles as can be seen by the presence of white cementitious gel around the soil matrix. As can be observed in Figure 7, there are only smaller pores appearing after the soil treatment which indicates that the lime and fibre help in coating the agglomerate particles thus increasing the strength of the soil. Other than that, this is due to the reaction between the soil and fibre in filling the voids inside. The filling of the voids is attributed to the significant increase in strength similarly noted by [52], in soil treated with 6% of lime at 28 days curing periods, causing an increase in strength with a reduction in the coefficient of permeability. The surface treatment with 5% lime and the inclusion of fibre shows a significant result from the untreated soil in Figure 6 which improves the mechanical properties due to the development of the C-A-S-H compound that covered the surface area. Figure 8a,b shows micrographs of the fly ash and soil treated with AA, respectively. The microstructural of fly ash illustrated in Figure 8a shows that there is an irregular round shape  
Figure 6: FESEM images for untreated soil. Figure 7: FESEM images for treated soil with inclusion of fibre (CLF). (**a**) Compacted soil matrix with treated lime and fibre, (**b**) Soil particles were coating by white cementitious gel. FESEM images for treated soil with inclusion of fibre (CLF). particle. As the fly ash particles mixed with the activator (Figure 8b) shows a distributed spherical shape attributed to having bonded with the parent soil. The AA with the fibre binds and coats together with the aggregated soil particles thus leading to a compacted and dense structure that reflects in consumption of the cementitious gel filling inside the voids. Although there are still some voids or pores appearing as in Figure 8b, the soil matrix shows an increase of the soil strength with the absence of the additive relative to the untreated clay soil. This can be confirmed by the UCS result for the treated soil with alkaline activation for 28 days curing periods. Other than that, this can also be supported with the EDX analysis (Table 7) result where the chemical composition of Si and Al elements were detected in the alkaline activator treated clay soil, as clearly seen in Figure 8 which signals that the alkali activator had taken place in treated clay soil with the presence of SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) in the soil lime and alkaline activator. The result signifies that large voids in the untreated soil (Figure 6) have diminished with the filling of fly ash and lime in those voids with the admixtures. As it can be seen, the formation of SI-O-Al and Si-O-Si bonds occurs from the dissolution of the fly ash contributing to the overall aluminosilicate gel, typically low- Ca AA blends.