Microdust effect on the physical condition and microstructure of tropical black clay

Abstract

An industrial waste product, microdust, was applied in this study to investigate its effect on the compaction characteristics and microstructure of tropical black clay (TBC) soil. The additive was added in percentages of 5%, 10%, 15% and 20%, by weight of the air-dried soil and tests were done to determine the optimum moisture content (OMC) and maximum dry density (MDD) at three compactive efforts. Microstructural tests including scanning electron microscopy (SEM) and energy dispersive spectroscopy were conducted to study the morphological changes in the soil microfabric after 14 days curing. The first batch of tests was conducted on mixtures of the TBC and microdust at 10% and 20% each. Then, the second batch of tests was done on mixtures of TBC, 4% lime and microdust at 10% and 20% separately. Otsu multi-thresholding and watershed segmentation algorithms were used for the SEM imaging analysis of the natural and treated soils. Results obtained from this study showed respective increase and decrease in MDD and OMC with increase in compactive effort and microdust content, which was found to be statistically significant based on analysis of variance. Microstructural analyses suggest that the microdust exhibits filler effect and cation exchange process, which helps to improve the soil behavior. Furthermore, cementitious compounds were formed in soil-lime-microdust mixtures indicating pozzolanic reaction. The SEM imaging analysis revealed substantial reduction in soil porosity for both soil-microdust and soil-lime-microdust mixtures, which underlines the stabilization potential of the additive. The best combination of the additives was found at 4%lime and 10%microdust.