The Effect of Groundnut Shell Ash on the Geotechnical Properties of Lateritic Soils
1,* Adeniyi, I.A., 1Olabiyi, Y.A., and 1 Ogundalu, A.O.
1, Department of Civil and Environmental Engineering, University of Lagos, Akoka,Yaba, Lagos State, Nigeria
DOI: 10.36108/laujoces/5202.41.0150
Abstract
This study explored the effect of groundnut shell ash (GSA) on the geotechnical properties of lateritic soil collected from Imota, Ikorodu, Lagos State, Nigeria. The natural soil was classified as A-2-7 (Group Index = 6) under the AASHTO system and SC (Silty Clayey Sand) under the USCS system, indicating it was a fair subgrade material. GSA was blended with the soil at concentrations of 0, 2, 4, 6, and 8% by dry weight, and the modified soil was tested for Atterberg limits, compaction characteristics, California Bearing Ratio (CBR), and Unconfined Compressive Strength (UCS). The Atterberg limits demonstrated that the plasticity index (PI) marginally declined from 20.31% (0% GSA) to 19.02% (8% GSA), indicating lower soil plasticity, while the liquid limit (LL) varied with GSA addition, peaking at 52.64% (6% GSA) and falling to 42.21% (8% GSA). The maximum dry density (MDD) declined from 1.621 g/cm³ (0% GSA) to 1.57 g/cm³ (6% GSA) but then slightly increased to 1.6 g/cm³ (8% GSA), according to compaction experiments conducted using British Standard Light (BSL) energy. A drop in the optimal moisture content (OMC) from 19.48% (0% GSA) to 17.63% (6% GSA) indicates better compaction properties. Significant strength enhancement was shown by the California Bearing Ratio (CBR) tests, where the wet CBR increased from 8.23% (0% GSA) to 24.66% (8% GSA) and the unsoaked CBR increased from 9.73% to 26.74%. According to Unconfined Compressive Strength (UCS) tests, strength significantly increased, going from 70.29 kN/m² (0% GSA) to 313.33 kN/m² (8% GSA). This study shows that groundnut shell ash (GSA)-treated lateritic soils are excellent subgrades and could possibly be used as a subbase material for light-traffic highways.
Keywords: Groundnut shell ash, Soil stabilization, Lateritic soil, Atterberg limits, Compaction, California Bearing Ratio, Unconfined Compressive Strength