Optimization of Fly Ash Dosage in Silty Soil through Geotechnical and Microstructural Characterization

Abstract

Sustainable recycling of industrial by-products for soil improvement is a viable solution for geotechnical engineering and waste disposal problem. The coal fly ash which is a byproduct from water powered plants is used in this study to study the engineering and microstructure properties of fly ash reinforced silty soil. Fly ash was mixed with a soil in 20%, 30%, 40% and 45% dry contents by weight and the blended mixtures were characterised by grain size distribution method, Standard Proctor compaction method and shear strength tests. The results revealed that fly ash has a significant effect on the behaviour of soil and 40% fly ash content showed the best performance. This dosage provided the good compaction properties and peak shear strength for the stabilised soil. Scanning electron microscopy (SEM) analysis was performed to gain insight into the mechanisms responsible for these benefits. Results showed denser soil matrix under optimum fly ash content, [13] SEM micrographs obtained at each mixing period indicated diagenesis from particles coalescence to improved particle interlocking and bonding between the siliceous soil particles with less pore spaces at maximum fly ash content. The correlation between geotechnical and microstructural observations substantiates the effectiveness of fly ash in enhancing the performance of silty soil. The results indicate that 40% fly ash is the optimum dosage for stabilisation and emphasise the potential of using fly ash as a sustainable and economical material for ground improvement applications.