Stabilization of Black Cotton Soil Using Groundnut Shell Ash


T.S. Ijimdiyaa, A.L. Ashimiyu, D.K. Abubakar

Department of Civil Engineering, Ahmadu Bello University
Zaria, Nigeria
a: Corresponding author ; e-mail:, a



Laboratory studies to investigate the possibility of utilizing Groundnut Shell Ash (GSA) as a stabilizing agent to improve the engineering properties of black cotton soil was carried out. Black cotton soil is classified as A-7-6 in accordance with AASHTO soil classification system. Groundnut shell is an agricultural waste product obtained from the milling of groundnut. The groundnut shell are found extensively in the northern part of Nigeria where they are cultivated. The results obtained show that the moisture- density relationship follows a trend of increasing optimum moisture content (OMC)/decreasing maximum dry density (MDD) at the standard Proctor compaction energy. California bearing ratio (CBR) values obtained are lower than the 80% CBR criterion recommended for untreated base course materials. The peak CBR value obtained was 6% at 8 % GSA. This value did not meet the recommended criterion for subgrade materials. The unconfined compressive strength (UCS) at 7 days is lower than the 1034.25 kN/m2 evaluation criterion recommended by TRRL (1977) for adequate stabilization. It is therefore recommended that groundnut shell ash could be used as an admixture with a more potent stabilizer compacted at standard Proctor compaction in order to reduce the cost of stabilization.

Keywords: Groundnut shell ash, optimum moisture content, maximum dry density, unconfined compressive strength, California bearing ratio.

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