Characterization and Volumetric Stability of High-Plasticity Clay Stabilized by Fly Ash and Metakaolin Based Geopolymers

Volume 12 , Issue 2 , May 2026 , Pages 312-328

Authors

Zahraa Rashid 1 ; Chra Othman Mahmood 1

1 Koya University, Department of Geotechnical Engineering, Faculty of Engineering, Koya, KR, Iraq

DOI logo 10.17656/sjes.10213

Keywords

Abstract

This study aims to characterize and analyze the physical and chemical performance of CH clay soil stabilized independently and separately by fly ash and metakaolin based geopolymers activated by sodium hydroxide. Different percentages up to 18% of both geopolymers were considered to assess how they affect soil plasticity, compaction and volumetric stability. The X-ray fluorescence (XRF) analysis for soil and binders were conducted to assess aluminosilicate amounts necessary for geopolymer formation and to support the observed results. The results of Atterberg’s limits and compaction tests showed a decrease in soil plasticity and increase in maximum dry density of soil with increase in geopolymer content. Durability was evaluated through one-dimensional swelling-shrinkage cycles, where higher binder contents resulted in pronounced volume change reduction and hence improvement of dimensional stability due to moisture changes. Scanning electron microscopy analysis showed a dense and compact matrix with continuous geopolymer gel formation and enhanced interparticle bonding. The findings of these tests show that sodium hydroxide activated geopolymer binders can alter the physio-chemical properties and matrix of clay soil to improve its dimensional stability and wetting-drying cycle durability.

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