Study on the Geotechnical Properties of Lateritic Soil Stabilized With Bentonite and Groundnut Shell Ash as Admixture for Clay Liner in Waste Containment

Waste management in Nigeria is characterized by poor landfilling practices in low-lying areas with improper planning of waste dumping. Whenever the soil on site is unfit for a barrier, it is blended with conventional stabilizers, but these additives are costly, hence the need to partially replace them with cheaper materials to achieve the desired results is essential. Consistency limit and engineering properties tests were conducted on the virgin and treated soil specimens. The Bentonite was added at a constant ratio of 6% whilst the groundnut shell ash was increased in the ratio of 0%, 2%, 4%, 6%, 8% and 10%.  Samples were prepared at a moulding water content of (-2% ≥ OMC ≤ 4%), adopting BSL and BSH energy levels. Preliminary laboratory test on the natural soil indicated that the soil is A-4(3) and SM according to AASHTO and USCS classification systems, respectively. From the compaction test carried out, it was observed maximum dry density (MDD) increases and optimum moisture content (OMC) decreases upon stepped addition of Groundnut shell ash (GSA). Hydraulic conductivity, volumetric shrinkage strain and UCS values recorded at 6% bentonite/ 6% groundnut shell ash content gave satisfactory results that met the acceptable values of ≤ 1× 10-9 m/s, ≤ 4%, and ≥ 200 kN/m² for BSL and BSH energy levels, respectively. The overall acceptable range for groundnut shell ash stabilized bentonite-lateritic soil was obtained at 6% bentonite/ 6% groundnut shell ash blend for samples prepared at moulding moisture content of 19.5 – 21.0% and 16.5 – 20.0% respectively. Investigation of leaching capability of groundnut ash into the environment using batch equilibrium test showed that the desorbed values of iron and pH for the optimally modified soil falls within the acceptable values endorsed by the Nigeria industrial standard (NIS) and world health organization (WHO).