Influence of Fly Ash-Based Geopolymers on Treated-Contaminated Soil Properties

Using natural soil in landfill sites for landfill construction is common in developing countries such as Indonesia. However, the risk of contaminated soil being used as material needs to be reduced by soil improvement to meet the landfill base requirement. Geopolymer is one stabilization material with high durability towards the contaminants, in which fly ash is one of the best geopolymer raw materials due to its readily great supplies and noble properties. The present study investigates fly ash-based geopolymer (FAG) influence on the treated-contaminated soil properties specifically for landfill liner purposes. The studied soils were collected from Ngipik Landfill, an indiscriminate municipal landfill in Gresik, East Java-Indonesia. The samples were obtained from three different locations around the waste mound and stabilized with FAG at 5, 10, and 15 wt.% of unstabilized soil at its optimum water content compared to the natural soil. The laboratory-scale tests were conducted, including the unconfined compressive strength test, standard compaction proctor, consolidation test, and the permeability test to understand the treated-soil characteristics better. The Scanning Electron Microscope (SEM) analysis was gathered to examine the treated soil's micro-properties. The results denoted that the FAG addition increases the soil's compressive strength up to 36% and reduces the compressibility to up to 60%. The permeability shows a slight decrement in 5% and 10% of FAG addition. The SEM image indicates that the FAG made bonds and fills the void. This study concludes the FAG enhances the mechanical properties of Ngipik Landfill soil despite the contamination.