An Evaluation of the Influence of Corn Cob Ash on the Strength Parameters of Lateritic Soils

Abstract

This paper reports the investigation of Corn Cob Ash as a pozzolan and a stabilizing agent for lateritic soils in road pavement construction.  Corn cob feedstock was obtained from Maya, a rural community in the derived savannah agro-ecological zone of South-Western Nigeria, and burnt to ashes of pozzolanic quality. Reddish brown silty clayey sand material, characterized as an A-2-6(3) material and  locally recognized as laterites was obtained from a borrow pit in Abeokuta, South-Western Nigeria and subjected to physical characterization tests according to BS 1377: 2000. The soil was subsequently mixed with CCA in varying percentages of 0%, 1.5%, 3%, 4.5%, 6% and 7.5% and the influence of CCA on the soil was determined for Liquid Limit, Plastic Limit, Compaction Characteristics, CBR and the Unconfined Compression Test. These tests were repeated on laterite-CCA-cement mix and laterite-cement mix respectively in order to detect any pozzolanicity in CCA when it combines with Portland cement and to compare results with a known soil stabilizing agent.  The result shows a similarity in the compaction characteristics of soil-cement, soil-CCA and soil-CCA-cement, in that with increasing addition of binder from 1.5% to 7.5%, Maximum Dry Density progressively declined while the OMC steadily increased. In terms of the strength parameters, the maximum positive impact was observed at 1.5% CCA addition for soil-CCA with a CBR value of 84% and a UCS value of 1.0MN/m2, compared with the control values of 65% and 0.4MN/m2 respectively. For the soil-CCA-cement mix, the strength parameters CBR and UCS continued to increase with increasing binder addition within the tested range for the ratios 1:2 and 1:1 and 2:1 CCA:cement. Significantly, the results from the soil-CCA-cement mix, indicate the pozzolanicity of CCA in that UCS values were higher by at least 14% for the 1:1 ratio, than was attained with the addition of only the corresponding quantity of cement.

Keywords: Corn Cob Ash, pozzolan, CBR, UCS, biomass waste, road pavement.