Investigating the Potential of Groundnut Shell Ash as a Cementitious Supplement in Enhancing the Engineering Properties of Lateritic Soil

There has been a lot of global research on the economically effective use of wastes for engineering applications as a result of the need to lower the cost of waste disposal and the rising expense of soil stabilizers. This study investigates the performance of Groundnut Shell Ash (GSA) as a supplementary material to cement in the stabilization of lateritic soil, with the aim of enhancing its engineering properties for geotechnical applications. The experimental program involved the characterization of lateritic soil blended with varying GSA contents (0%–6%) and evaluation through geotechnical, chemical, mineralogical, and strength tests. Results reveal that the specific gravity of the soil decreased with increased GSA content due to the ash’s lower density, although values at 2%–4% remained within acceptable limits. Plasticity characteristics were moderately affected; the plasticity index decreased significantly at 6% GSA, indicating reduced soil plasticity and improved workability. The California Bearing Ratio (CBR) test results showed a significant improvement in soil strength with GSA addition, with maximum CBR (48%) recorded at 4% GSA, exceeding the minimum standard of 30% for sub-base materials. Statistical analysis further confirmed a strong positive correlation (r = 0.997) between GSA content and CBR, validating GSA’s efficacy in enhancing load-bearing capacity. The regression equation shows that at 0% GSA, the CBR value is reduced by 7.333% from the base intercept (41.33%), reflecting the unmodified lateritic soil's lower strength. As 2% GSA is added, the CBR slightly improves by 0.6667%, while at 4% GSA, the improvement becomes more significant with a 6.667% increase. This trend suggests that GSA has a positive effect on soil strength when used moderately, particularly at 4% replacement