Evaluation of Geotechnical Properties of Pond Ash-Bentonite Mixture as a Potential Landfill Liner Material

Landfill liners are crucial in preventing the migration of contaminants by blocking the flow of leachate. Although clay liners are commonly used owing to low permeability, they are susceptible to cracking and shrinking during unsaturated states, which can lead to leachate leakage. To address this, alternative materials with low permeability and shrinkage potential are needed. Treated pond ash, a by-product of coal combustion containing fine sand-sized spherical particles, shows potential as the landfill liner material. This study examines the geotechnical properties of pond ash-Bentonite mixtures as potential liner materials. Mixtures with different Bentonite percentages (0, 2, 4, 6, 8, 10, 12, 14, 16, and 18%) were tested using various experiments like liquid limit, plastic limit, consolidation, and unconfined compression tests. The results display that the Bentonite addition significantly increases the plasticity index and thus the water-holding capacity of pond ash. The unconfined compressive strength of this mixture increased by 64% with the addition of Bentonite up to 8%, and then, it reduced with further Bentonite addition. The consolidation tests displayed that the hydraulic conductivity of raw pond ash decreased below 10−9 m/s by adding Bentonite, indicating that pond ash-Bentonite mixtures have low permeability and can be suitable as landfill liner materials.