ABSTRACT
This study investigates the effectiveness of bentonite-amended flyash (BAF) liners as barriers against infiltration in municipal solid waste (MSW) landfills. Laboratory experiments were conducted to evaluate the compaction properties and hydraulic conductivity (HC) of the BAF liners with varying mix proportions. Flyash, a byproduct of coal-fired power plants, amended with bentonite was utilized as a cost-effective alternative to conventional clay liners. Bentonite, a highly expandable clay mineral, was incorporated to enhance hydraulic performance. Standard Proctor compaction tests were performed to determine optimal compaction properties of different BAF mixes. Further, BAF specimens with different mix proportions were prepared by compacting at maximum dry density (MDD), and optimum moisture content (OMC). HC tests were performed on the compacted samples using a flexible-wall (triaxial) permeameter apparatus following ASTM standards. Compaction test results revealed that a mix ratio of 80:20 (Flyash: Bentonite) resulted in highest MDD and lowest OMC. Results also revealed a significant reduction in HC upon the addition of bentonite to the BAF liner. As the bentonite content increased, the HC decreased, indicating improved barrier properties. The optimal performance was achieved with a bentonite content of 20-30%, resulting in good compaction properties (high MDD and low OMC), and a HC below the regulatory limit of 10-7 cm/s, rendering the mix proportion optimal for barrier application. Overall, this study highlights the potential of BAF liners as efficient and cost-effective barrier systems for MSW landfills. The significant reduction in HC because of bentonite amendment, and excellent heavy metal and nutrient adsorption capabilities of flyash renders BAF effective for application as a barrier material in landfills.
