Effect of groundnut shell ash on the particle size and plasticity characteristics of black cotton soil

The paper presents the results of a laboratory study on the effect of groundnut shell ash on the particle size distribution and plasticity characteristics of black cotton soil. Black cotton soil was treated with a maximum 10 % groundnut shell ash by weight of dry soil. The results show that there was a substantial reduction in the amount of fines content with higher doses of groundnut shell ash. The percentage of silt fraction in the natural soil was 91 % and on treatment with maximum 10 % groundnut shell ash content (by weight of dry soil) at optimum moisture content (OMC), the silt fraction was reduced to 1.3 %. The plasticity index increased from 38 to 75 % when treated with 10 % groundnut shell ash content by weight of dry soil. The results obtained place the soil below the Highway Research Board of America (1943) requirements of plasticity index of less than 50 %. The plasticity modulus (PM), plasticity product (PP) and the shrinkage modulus (SM) increased while the grading modulus (GM) decreased with higher doses of groundnut shell ash. However, the treated soil can be admixed with more potent stabilizer since its workability was improved by addition of 10% groundnut shell ash content by dry weight of soil.