Investigating the Effect of Silica Fume on the Engineering Behavior and Microstructure of Clay Liners

چکیده مقاله

Clay liners are widely used in landfill systems to prevent the migration of contaminants into the surrounding soil and groundwater by providing low permeability and adequate mechanical stability. Various stabilizing agents have been investigated to enhance the engineering performance of these clayey soils, particularly materials that are economical, readily available, and capable of participating in pozzolanic reactions. Limited attention has been given to the application of silica fume, a highly fine amorphous silica produced as a by-product of silicon or ferrosilicon alloy manufacturing, in clay liner systems. In this study, the influence of silica fume contents of 5%, 10%, and 15% (by dry weight of soil) on the behavior of high-plasticity clay was evaluated through standard compaction, unconfined compressive strength, free swell, and permeability tests. The experimental results showed that increasing silica fume content decreased maximum dry density, permeability, swelling percentage, and swelling pressure, while increasing optimum moisture content and unconfined compressive strength. The specimen containing 15% silica fume exhibited more than a 50% reduction in permeability and achieved compressive strength values exceeding the minimum recommended for clay liner materials. In addition, swelling pressure decreased by more than 30% at this dosage. Microstructural observations obtained from scanning electron microscopy confirmed the development of a denser and more compact soil matrix following silica fume treatment.