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<p>Ordinary Portland cement (OPC) has been utilized for stabilizing soft soils; however, the energy-intensive nature of OPC production, coupled with its susceptibility to shrinkage cracking and ettringite formation, renders OPC an unsustainable stabilization method. The use of alkali-activated geopolymers for soil stabilization has emerged in recent years, but there is a significant lack of research on the optimal mix for stabilizing expansive soils with low calcium fly ash (FA) based geopolymers that achieve high strength and low swell characteristics. Further, while mix designs for geopolymer curing at elevated temperatures exist, ambient curing conditions would be more favorable for a pragmatic binder. Therefore, this study aims to determine the optimal expansive soil-geopolymer (ES-GP) mix cured at ambient temperature, focusing on strength and swell characteristics. The effects of activator content, binder content, and NaOH molarity on the strength and swell characteristics of ES-GP were analyzed. ES-GP samples with different activator/binder ratios (0.2–0.5), binder/soil ratios (0.1–0.4), and NaOH molarity values (6–12&#xa0;M) were prepared. Mechanical, swell, and microstructural investigations on the treated specimens were carried out using unconfined compressive strength (UCS) testing, constant volume swell pressure testing, and scanning electron microscopy (SEM) analysis. The results revealed that the optimal mix ratios for higher strength and reduced swell characteristics include an activator/binder ratio of 0.4, a binder/soil ratio of 0.3, and an NaOH molarity of 8&#xa0;M, resulting in a UCS increment of 550% and a swell pressure reduction of 25% compared to the raw soil. Overall, low calcium FA-based geopolymers present a promising alternative to OPC-based binders for stabilizing expansive soils under room temperature curing conditions.</p>

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Strength and swell characteristics of low calcium fly ash based geopolymer stabilised expansive soil

  • 期刊论文

  • 发表日期：

    2025年12月13日

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  • S. Kanjana,
  • S. Sajiththijan,
  • M. C. M. Nasvi,
  • M. M. A. L. N. Maheepala

摘要

Ordinary Portland cement (OPC) has been utilized for stabilizing soft soils; however, the energy-intensive nature of OPC production, coupled with its susceptibility to shrinkage cracking and ettringite formation, renders OPC an unsustainable stabilization method. The use of alkali-activated geopolymers for soil stabilization has emerged in recent years, but there is a significant lack of research on the optimal mix for stabilizing expansive soils with low calcium fly ash (FA) based geopolymers that achieve high strength and low swell characteristics. Further, while mix designs for geopolymer curing at elevated temperatures exist, ambient curing conditions would be more favorable for a pragmatic binder. Therefore, this study aims to determine the optimal expansive soil-geopolymer (ES-GP) mix cured at ambient temperature, focusing on strength and swell characteristics. The effects of activator content, binder content, and NaOH molarity on the strength and swell characteristics of ES-GP were analyzed. ES-GP samples with different activator/binder ratios (0.2–0.5), binder/soil ratios (0.1–0.4), and NaOH molarity values (6–12 M) were prepared. Mechanical, swell, and microstructural investigations on the treated specimens were carried out using unconfined compressive strength (UCS) testing, constant volume swell pressure testing, and scanning electron microscopy (SEM) analysis. The results revealed that the optimal mix ratios for higher strength and reduced swell characteristics include an activator/binder ratio of 0.4, a binder/soil ratio of 0.3, and an NaOH molarity of 8 M, resulting in a UCS increment of 550% and a swell pressure reduction of 25% compared to the raw soil. Overall, low calcium FA-based geopolymers present a promising alternative to OPC-based binders for stabilizing expansive soils under room temperature curing conditions.