Investigation of Fly Ash-Bentonite Mixture as Waste Containment Liner under Wetting-Drying Cycles

Desiccation cracks in clay soils are a serious problem in landfill liner. This study aims to evaluate the behaviour of soil cracks in fly ash-bentonite mixtures as land-fill lining materials under wet-dry cycles and analyse the crack intensity using a quantitative approach in the form of Crack Intensity Factor (CIF). The methods used in this study include laboratory testing of three variations of soil composites consisting of fly ash, bentonite, and coconut fiber. Each variation was tested through swelling test, Standard Proctor, permeability test, and desiccation crack test simulated in temperature-controlled compaction tanks (25°C and 40°C) for 15 days. Visual and quantitative analyses of CIF were performed by periodic im-aging and processing using MATLAB software. Results showed that the composite with the highest bentonite content (V1) showed the largest CIF value (2.94% at 40°C and 0.38% at 25°C), while the composite without bentonite (V3) had the lowest CIF value (0.138% at 40°C and 0% at 25°C). In summation, material adding with bentonite and coconut fiber can decrease the desiccation crack significantly due to elasticities modulus, to absorb deformation before spreading the crack. Furthermore, the use of wetting-drying cycle as a method and measured by CIF to analyse the morphology crack are beneficial to assess the variation sample.