Effect of Cashew Nut Shell Ash on Volumetric Shrinkage of Compacted Clay Soil

Abstract

Hydraulic conductivity value of a compacted clay soil can rise above the minimum regulatory value during desiccation thereby induces large cracks in an engineered landfill. In the quest to reduce the degree of cracking that will be generated dues to the volumetric shrinkage of the compacted clay soil, which in turn will reduce the amount of leachate that will be percolating into the underground water system, an investigation was performed by treating a clay soil with up to 16% Cashew Nut Shell Ash (CNSA) content using three compactive efforts (Standard proctor (SP), West African standard (WAS) and Modified Proctor (MP)) at -2, 0, 2 and 4% of optimum moisture content (OMC). Samples were extruded from the compaction moulds and placed on the laboratory table to air dry for 30 days at a uniform regulated temperature of 27 ± 2^Oc in order to evaluate the suitability of the material for the construction of cover and liner in an engineered landfill. Results indicated that the OMC and maximum dry density (MDD) increased with higher CNSA treatment.  Volumetric shrinkage strain (VSS) increased with; higher CNSA, higher molding moisture content and moisture content relative to the optimum. Effect of CNSA on the soil showed that all specimens prepared at 2% dry of optimum to 4% wet of optimum for 4% and 8% soil-CNSA mixtures for the three compactive efforts, met the maximum allowable regulatory VSS criterion of4%, thus making the material suitable for the construction of cover and liner in waste dumping ground.