Optimization of bagasse ash content in cement-stabilized lateritic soil

Thesis Abstract

The frequent rises in the price of cement and other binders have resulted in the escalation of the cost of construction, rehabilitation and maintenance of roads. One of the possible ways of cost reduction is to convert waste bagasse residue into ash and use it as a supplement/partial replacement for cement. Therefore this study is an attempt to optimize bagasse ash content in cement-stabilized lateritic soil for low-cost roads. The bagasse ash and lateritic soil were characterized by carrying out Atomic Absorption Spectrometer and soil preliminary tests as well as X-ray diffraction respectively. Compaction test, California bearing ratio, unconfined compressive strength and durability tests were carried out on the soil stabilized with 2%, 4%, 6% and 8% cement contents and bagasse ash ranging from 0% to 20% at 2% intervals; all percentages of the bagasse ash and cement were by the weight of dry soil. Cost analysis was carried out for the constituents of the stabilized material and a model was formed for cost evaluation. Also three regression models were developed that involved relationships of cost of bagasse ash, cement content, optimum moisture content, California bearing ratio and unconfined compressive strength at 7 days curing period. The three regression models were used to form a non-linear model which was linearized and solved with the simplex method including sensitivity analysis on the objective function and the constraints. Attempt was also made to apply Scheffe’s regression method from obtained results. It was observed that the increase in bagasse ash content increased the optimum moisture content but reduced maximum dry density. On the other hand higher bagasse ash tremendously improved the strength properties of the stabilized matrix. The optimum contents for bagasse ash, cement and optimum moisture content for an economic mix were 14.03%, 4.52% and 22.46% respectively at a cost of 39.50 kobo for stabilizing 100 grams of the lateritic soil as against 43.52 kobo for stabilizing with only cement.