Microstructural Characterization of Lateritic Soil Stabilized with Nano-Silica and Plantain Peel Ash: SEM, EDX, and XRD Analysis

Using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD), this study examines the microstructural changes of lateritic soil stabilized with plantain peel ash (PPA) and nano-silica (NS) from Ibienafe, South Ibie, Edo State, Nigeria. Sample 1 (2.5% PPA), Sample 2 (5.0% PPA), Sample 3 (2.5% NS), Sample 4 (5.0% PPA + 2.5% NS), and Sample 5 (5.0% NS) were the five dry weight soil mixes that were made. With extensive calcium silicate hydrate (C-SH) and calcium aluminate hydrate (C-A-H) gel formation, needle-like crystalline bridges, and few voids, Sample 4 showed the densest matrix, according to SEM analysis. This indicated strong pozzolanic bonding. EDX verified that Sample 4 had low carbon (3.70%) and high silica (15.45%) and alumina (16.46%), indicating optimal reactivity. Friedelite and DAP-O12 were detected by XRD in Sample 4, indicating advanced aluminosilicate bonding, whereas inert quartz and kaolinite were found in Samples 1 and 2, indicating limited pozzolanic activity. Although Sample 5 contained trace actinolite, indicating possible long-term durability concerns, Samples 3 and 5 showed cristobalite and alite, confirming silica-driven cementation. In Sample 4, the synergistic combination of 5.0% PPA and 2.5% NS produced the most robust microstructure and the highest California Bearing Ratio (48.55%), providing a sustainable and environmentally friendly method of lateritic soil stabilization for geotechnical applications. These results demonstrate how well agro-waste and nanomaterial blends can improve soil performance while supporting environmentally friendly building techniques.