Effect of Neem Seed Ash on the Geotechnical Properties of Lateritic Soil

The impact of Neem Seed Ash (NSA) on the geotechnical properties of three clay soil samples classified as MH and CH by the Unified Soil Classification System is investigated in this study. The results of preliminary testing indicated moderate plasticity and load-bearing capacity, with natural moisture levels ranging from 7.2% to 9.38%, specific gravities from 2.66 to 2.75, and California Bearing Ratio (CBR) values from 13.42% to 19.8%. According to ASTM C618’s Class C classification, NSA's pozzolanic content of 52.01% was determined by chemical analysis. The engineering properties of the soils were significantly improved by NSA integration. As the NSA content rose, the specific gravity decreased, demonstrating the admixture's decreased density. Indicating improved soil workability and decreased plasticity, Atterberg limits showed a significant decline: liquid limits decreased from 37% to 12%, plastic limits from 27% to 11%, and the plasticity index from 14% to 2%. The maximum dry density increased to 2.37 g/cm<sup>3</sup> at 6% NSA substitution, according to compaction tests, and the optimal moisture content decreased from 16% to 9.6%, indicating increased compaction efficiency. With 8% NSA replacement, the CBR values increased dramatically, reaching 44.1%, indicating a notable improvement in strength. These findings confirm that NSA is an effective stabilizing agent for difficult clay soils, enhancing their mechanical properties and potentially reducing environmental impacts and building costs. The study supports the use of NSA as an economical and environmentally friendly additive for stabilizing geotechnical soil.