Stabilization of Expansive Clay Using Lime and Sugarcane Bagasse Ash

Abstract

The scarcity and rising cost of traditional stabilizers like Lime and Cement has led to the research into  clay soil stabilizing potential of bagasse ash that is cheaper, readily available and environmental friendly and ha s a serious disposal problem.  Bagasse is a fibrous residue of sugar cane stalks that remains after extraction of sugar and when incinerated gives the ash. The chemical analysis on bagasse ash carried out at the Ministry of Mining Kenya was found to contain mainly silica, and potasium, iron, calcium, aluminium, magnesium as minor components and exhibit pozzolanic properties. The research investigated the properties of expansive clay soil when stabilized by lime, ash and combination of lime and ash. The experiment covered grading test, Plasticity index (Atterberg) and California bearing ratio (CBR). First, particles size distribution was determined from grading test, secondly varying percentages (4%, 5%, and 6%) of lime was used to stabilize clay soil and then plasticity and CBR were determined. The same procedure was repeated for bagasse ash and finally the varying mix ratios of lime and ash 1:4, 2:3, 3:2 and 4:1 were used on the sample. The PI of the stabilized clay soil decreased with increase in the quantity of lime, ash and ratio lime to ash in all the samples. The addition of lime or bagasse ash helps to reduce the shrinkage and swelling behavior of soil hence reduction in plasticity. The plasticity reduction in this study was quantified using the linear shrinkage and swelling tests. The california bearing ratio increased remarkably with increase in lime quantity added but decreased for bagasse ash. The combination of lime and ash gave good results that meet the set standard by road design manual part III of minimum CBR of 20 for sub base road. From the results of swelling, negligible shrinkage and poor CBR values; it was concluded that sugarcane bagasse ash cannot singly be used in stabilisation of expansive clay soil. It was found that both lime and bagasse ash reduced the linear shrinkage, however, the addition of lime reduced the linear shrinkage to a greater degree than the same percentage of bagasse ash. When lime and bagasse ash are combined at the optimum ratio of 4:1, the stabilisation results conforms with the  set standard of California bearing ratio of 36, plasticity index 20, Linear shrinkage of 9.0, negligible swelling.

Key words: Clay soil, sugarcane bagasse ash,  Lime, stabilization, Plasticity Index, CBR,