Soft clay has become the main problem of the Waste Facility Development Project on the North Coast of Lamongan, East Java, Indonesia. The soil has a high plasticity index, high moisture content, small shear strength, and low permeability. Therefore, stabilization efforts to improve the soil characteristics are needed to support the construction. Research on soil stabilization using fly ash has been widely conducted. Yet, there have just been a few studies conducted on soil stabilization using fly ash activated by alkaline or geopolymer. This paper compares soil stabilization using fly ash and soil stabilization using fly ash activated with geopolymer. The results show that soil stabilized by fly ash generally has better characteristics than fly ash activated with geopolymer. However, the CBR test result of the soil stabilized with geopolymer-activated fly ash shows a higher value than the soil stabilized using fly ash. The molarity and the curing time of the specimen can be the causing factor. Microstructural analysis using SEM shows conditions of denser soil after it is stabilized with geopolymer. It indicates that the formation of a binder gel increases the interaction between the clay particles and the stabilizing agent.

Original languageEnglish
Pages (from-to)9-17
Number of pages9
JournalInternational Journal of GEOMATE
Issue number109
Publication statusPublished - 2023


  • Clay soil stabilization
  • Compressive strength
  • Fly ash geopolymer
  • Micropores


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