The world population has significantly increased at a high rate throughout the years leading to extreme competition of available natural resources and depletion of some resources thus there has been need for sustainable resources in our construction industry; resources that are eco-friendly, renewable, bio-degradable, cheap and also exhibit excellent engineering properties.
The world is keen in using sustainable resources through promoting and funding their Sustainable Development Goals 2030. Africa picking up these goals in their blueprint African Agenda 2063 to promote a prosperous Africa based on inclusive growth and sustainable development. Kenya has not been left behind as it focusses in promoting in manufacturing in Uhuru Kenyatta’s masterplan the Big Four Agenda which is a major component of Kenya’s Vision 2030.
Through the years, pavement subgrades have been stabilized using conventional methods by mostly cement, lime and other additives which are effective and efficient but are proving not to be sustainable in a world experiencing full blown development in the construction industry and demand of low cost, environmental friendly and viable materials. Soil stabilized with cement has also shown increase in shrinkage with increase in cement (Adam 2001). Sugarcane Bagasse Ash is a finished product of sugarcane which had its juices extracted and the bagasse combusted to form the ash. Bagasse ash, which is rich in oxides of silica and aluminum with marginally calcium oxides, has exhibited good pozzolanic properties suitable for soil stabilization. SCBA has become common in developing countries such as Kenya due to it being cheap, locally available, bio-degradable, renewable and promoting the country’s social economic background.
The research done was to determine the performance of bagasse ash as a red coffee soil subgrade stabilizer by using different ratios of the bagasse ash. Different methods of stabilization have been used throughout the years to improve the strength and reduce moisture content in soil in pavement design.
The research focused on bagasse ash, the mix proportions used, method of mixing and testing and drew results from the experiments carried out. Different ratios of bagasse ash were used with 0% being the control,2%, 4%, 6%, 10%, 12% were added to the soil as a percentage of dry weight of the soil. Experiments to determine the liquid limit, plastic limit i.e. Atterberg’s limits, optimum
moisture content, maximum dry density, and California Bearing Ratio were carried out using soil samples containing different percentages of bagasse ash.
From the research, it was found out that the red coffee soils treated with bagasse ash showed improved geotechnical properties of the stabilized red soil with percentage bagasse ash by weight of dry soil. The results of the study showed changes in moisture–density relationships resulting in lower maximum dry densities (MDD), higher optimum moisture contents (OMC) reduction in fine fractions with higher bagasse ash content in the soil – stabilizer mixtures. Bagasse ash treatment of red coffee soil yielded peak 7 days CBR values of 5.35% and13.3% at 2%and 12%, respectively though higher values were recorded at 10% which as 14.18%. It was concluded though bagasse ash reduced MDD, increased the OMC and increased the CBR, there was need of better results that meet the set standard by road design manual part III of minimum CBR of 20% for sub base road. The results of SCBA on MDD, OMC and low CBR values, it was concluded that sugarcane bagasse ash alone cannot be used to stabilize red coffee soils. However, need for improvement and further studies on SCBA as a soil stabilizer is recommended. Therefore, this study shows that bagasse ash can be effectively used to improve red coffee soils with low CBR values.