Silt soil is encountered in most parts of Rivers state and the preliminary investigation shows that it belongs to A-7-5 class of soil in the AASHTO soil classification system and generally has poor engineering properties. Traditional stabilizers like cement, lime and others have been efficient and effective in soil stabilization but their rising cost and negative impact to the environment has led to research into bagasse ash waste to be used as an alternative in soil stabilization. The study investigated the properties of silt soil when stabilized by lime, bagasse ash and combination of lime and ash. The research covered grading test, Plasticity Index (PI) and Rivers Bearing Ratio (RBR). 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 PI and RBR were determined. The RBR was carried out using Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) from graph of dry density against moisture content obtained from proctor test. The RBR results were as follows; lime (38%, 45%, and 50%), ash (6%, 4% and 2%), and ratio of lime/ash (19%, 27%, 30%, and 36%) respectively. The trend indicated that Rivers Bearing Ratio increased with increase in lime quantity added but decreased when bagasse ash was used. The combination of lime and ash gave good results that meet the set standard by road design manual part III of minimum RBR of 20 for sub base road. The results of ash on PI and low RBR values it was concluded that sugarcane bagasse ash alone cannot be used to stabilize silt 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 stabilization results of Rivers Bearing Ratio of 36, plasticity index 20, Linear shrinkage of 9.0, negligible swelling create a material that can used for construction works. Therefore, this study shows that lime in combination with bagasse ash can be effectively used to improve expansive soils with low soaked RBR value and high plasticity. It’s therefore recommended that since bagasse ash can partially replace lime in clay stabilization to form material with cementitious properties, the use of lime should be minimized to reduce creation of carbon dioxide. 

• Background to the Study 
Rivers state has poor road network system and is normally attributed to high cost of construction materials and silt soil which swell with little moisture and shrink in dry season. The solution to this problem is to create a cheaper construction material by improving the geotechnical properties of in-situ materials to reduce the overall cost. Stabilization process has been used to improve the properties of clay soil to attain engineering requirement but traditional stabilizers like lime and cement have became very expensive and their side effect to the environment have minimized their usage. The main focus of the study was on bagasse ash waste, a by-product which has a disposal problem in sugar factories. This research evaluated the effect of partial replacement of lime by sugarcane bagasse ash in stabilization of clay soil. 

Bagasse is defined as fibrous residue of sugar cane stalks that remains after extraction of sugar (Rainey, 2009). It is normally deposited as waste and it litters the environment. Most of the bagasse produced, amounting to one-third of all the cane crushed in some cases supplies the fuel for the generation of steam according to Bilba, Arsene, and Ouensanga, (2003) which eventually results in bagasse ash. The resulting ash is deposited in stockpiles which are normally dumped in waste landfills and constitute environmental problem to the society. When bagasse is left in the open, it ferments and decays, this brings about the need for safe disposal of the pollutant, which when inhaled in large quantity can result in respiratory disease known as bagassiosis (Laurianne, 2004). 

Bagasse ash is a pozzolanic material which is very rich in the oxides of silica and aluminum, and sometimes calcium Guilherme, Romildo, Eduardo, Luis, and Cristiano, (2004). Pozzolans usually require the presence of water in order for silica to combine with calcium hydroxide to form stable calcium silicate, which has cementitious properties. 

Lime is calcium oxide (CaO) or hydroxides of calcium and magnesium and is made by calcining limestone into either calcitic lime (high in calcium) or dolomitic lime (high in magnesium). Lime stabilization is the most widely used means of chemically for stabilizing unstable soils into structurally sound construction foundations. The use of lime in stabilization creates a number of important engineering properties in soils, including improved strength, improved resistance to fracture, fatigue, and permanent deformation, improved resilient properties, reduced swelling, and resistance to the damaging effects of moisture. 

Silt soils encountered in many construction sites in Rivers state have poor engineering properties. West (1995) defines expansive soils as those soils that consist of clays which shrink and swell with the primary clay being smectite (montmorillonite). Expansive soils affect the engineering structures because of their tendency to heave during wet season and shrink during dry season as per Mishra, Dhawan, and Rao, (2008). In order to make deficient expansive soils useful and meet geotechnical engineering design requirements, the process of stabilization is applied. Traditionally, the three most commonly used stabilizers are cement, lime and asphalt or bituminous compound; but the high cost of processing has made them expensive, deterring their usage. In order to mitigate this problem especially in developing countries, various possible alternatives to lime are considered along with other benefits that may accrue from these alternatives. Several waste materials such as Rice Husk Ash (RHA), Pulverized Fuel Ash (PFA), lime, Sugarcane Bagasse Ash (SCBA) and volcanic ash, are in use in many countries. There are basically two types of pozzolanas, namely natural and artificial pozzolanas. Natural pozzolanas are essentially volcanic ashes from geologically recent volcanic activity and artificial pozzolanas result from various industrial and agricultural processes, usually as by-products. The most important artificial pozzolanas are burnt clay, pulverized-fuel ash (PFA), ground granulated blast furnace slag (GGBFS) and rice husk ash (RHA). These admixtures (fly ash, cold bottom ash, crushed concrete powder, bagasse ash and blast furnace slag and phosphoric waste have been employed in research works by Osinubi, (1997) during soil stabilization. The aim of the study was to determine the effect of using SCBA to blend with lime to stabilize expansive clay. 

• Statement of the Problem 
Most parts of Rivers state are covered with silt soils which have poor engineering properties hence is not used during infrastructure development. Soils with desirable engineering properties must be transported from quarries which are many kilometers away hence raising the cost of construction. However, the transportation of large quantities of building material has negative impact on the environment and is not a sustainable practice. This has made roads in Rivers state are expensive to construct and maintain. The study used combination of lime and bagasse ash additives which are easily available to economically stabilize clay soils in Rivers state for use on roads, runways, and other similar applications. 

• Justification of the Study 
The State has an area of 3,032.2 sq. Km and lies between 1,200 and 1,800 meters above sea level. The population of Rivers is estimated at 1,630,934 (as projected in 2009) of which female constitute 52% while male are 48%. The major economic activity in the area is farming and business but the road network is in a poor state making it impossible for farmers to access the markets. The cost of improving roads is exorbitant due to clay soil which requires a replacement with imported materials or being stabilized. The traditional stabilizers like lime, cement etc are very expensive hence alternative means of using bagasse ash are sorted. The bagasse ash is ready available and has disposal problem with National environmental management Authority (Nema). A report by Yuko, (2004) on Nzoia Sugar Company indicated that the annual production of bagasse was 234,046 tons from the crushed cane of about 568,098 tons which is 40% of the sugar cane processed. About 85% of this bagasse is burned on site at the factories to generate steam for the evaporative extraction of sugar and some of it is also used to produce electricity for factory operations and sale to the local grid. 

• Objectives 
• General Objective 
To assess the effect of partial replacement of lime by sugar cane bagasse ash in stabilization of silt soil to produce sub-base layer material for road construction 

• Specific Objectives 
• To determine the chemical composition of the sugar cane bagasse ash 

• To determine physical and mechanical properties of silt soil stabilized with lime only and sugar cane bagasse ash only 

• To determine the amount of sugar cane bagasse ash required for partial replacement of lime for optimum silt soil stabilization. 

• Research Questions 
• What is the chemical composition of the sugar cane bagasse ash? 

• What are the physical and mechanical properties of silt soil stabilized with lime only and sugar cane bagasse ash only? 

• What is the amount of sugar cane bagasse ash required for partial replacement of lime for optimum silt soil stabilization? 

• Scope of the Study 
Reviewing literature pertaining to standardized laboratory procedures for preparing mixtures using traditional stabilizers. The scope included: 

• A classification of the soils by performing the following tests: natural water content, particle size distribution, Atterberg limits, moisture-density relationship using standard Proctor test and mineralogy of the clay soil. Other procedures for mixtures involving nontraditional stabilizers that have been studied previously by other researchers. 

• Developing a laboratory mixture preparation and testing procedure that can be used to evaluate and compare traditional and non-traditional stabilizers including bagasse ash. 

• Identifying the existence and significance of trends among base soil characteristics, and strength characteristics using the laboratory procedure developed. This study provides insight into how bagasse ash as stabilizer is effective for stabilizing clay soils commonly encountered in Rivers state. This report can be used as a guide to help in developing materials that can be used in road construction to improve the economy in the State. In addition, will solve a disposal problem for the company and hence reduce a pollution level that endangers the lives of people. 

• The Limitations 
The main research limitations are; 

• Lack of capital to carry out further research to ascertain some reactions like using more quantity of lime and bagasse ash. 

• Lack of equipment like combustion chambers where high temperatures of bagasse can achieved. 

• Lack of grinding machine that could have enabled the comparison between burnt and unburnt bagasse on PI and RBR

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