THE EFFECT OF FLY ASH AND PLASTIC FINES ON KAOLINITE CLAY

This study investigates the stabilization of kaolinite clay using fly ash and plastic fines. Disturbed soil sample was taken to the laboratory for examination. Laboratory experiments were conducted on the natural soil sample to characterize the soil and determine its mineralogical composition.Test result revealed that the soil is rich in kaolinite and the soil can be classified as A-7-5(21) and MH according to AASHTO and Unified Soil Classification System respectively. The soil sample is clayey soils with high plasticity, the soil is compressible and prone to volume changes at various moisture content. Stabilization was performed by mixing varying proportions (0-12%) of fly ash and plastic fines in a fixed ratio of 6 to 4. Results showed a marked improvement in engineering properties at optimum dosage of 10% for plasticity index (PI) and coefficient of permeability (k) while 8% and 6% for California bearing ratio (CBR) and Unconfined compression strength (UCS) respectively. Although the natural soil has the highest maximum dry density which can be attributed to lower material density of the additives compared to the specific gravity of the soil because the spaces to be occupied by the soil grains has been filled with the additives. The lesser the PI and k the better the soil is in terms of compressibility, volume changes and water absorption capacity. The CBR value increased significantly from 3.4% (natural soil) to 14.9%, indicating enhanced load bearing capacity. The UCS showed progressive strength gains over curing periods, with a peak of 248.3kN/m² after 28 days which is an indication of pozzolanic reaction which is time dependent. These findings demonstrate that the combined use of fly ash (FA) and plastic fines (PF) can effectively improve the geotechnical behavior of kaolinite clay, offering a sustainable and economically viable alternative to conventional stabilization methods. The study recommends the long term assessment of the combined blends of FA and PF soil mixtures and encourages further field trials and environmental assessments to support real-world applications.