Unconfined Compressive Strength and Damage Evolution in Geopolymer-Stabilized Clay Shale: Role of Temperature and Alkali Activator Ratio

Authors

  • Willis Diana Department of Civil Engineering, Universitas Muhammadiyah Yogyakarta, Yogyakarta, INDONESIA
  • Edi Hartono Department of Civil Engineering, Universitas Muhammadiyah Yogyakarta, Yogyakarta, INDONESIA
  • Agus Setyo Muntohar Department of Civil Engineering, Universitas Muhammadiyah Yogyakarta, Yogyakarta, INDONESIA
  • Nurza Purwa Abiyoga Department of Civil Engineering, Universitas Jambi, Jambi, INDONESIA

DOI:

https://doi.org/10.22146/jcef.22477

Keywords:

Alkali Activator Ratio, Clay Shale, Damage Properties, Geopolymer Stabilization, Temperature

Abstract

Exposed clay shale is highly susceptible to weathering and rapid strength degradation, which often leads to slope and earth-structure instability. Geopolymer-based soil stabilization has emerged as a promising method to improve the mechanical properties of such problematic materials. However, this chemical stabilization process is sensitive to environmental conditions, particularly temperature fluctuations. The performance of geopolymer-stabilized clay shale under elevated-temperature conditions remains insufficiently investigated, particularly in tropical regions such as Indonesia, where temperatures can fluctuate between 25◦C and 40◦C, and the exposed ground surface may reach up to 60◦C during the dry season because of intense solar radiation. This study evaluates the effectiveness of fly ash–based geopolymer in stabilizing clay shale under temperature variations ranging from 26◦C to 60◦C. A series of laboratory experiments was conducted using two alkali activator ratios (Na2SiO3:NaOH), namely 2.0 (Ratio A) and 2.5 (Ratio B). Mechanical performance was assessed through unconfined compressive strength (UCS) tests, stress–strain analysis, and energy-based damage evolution to quantify strength development and failure behavior. The results indicate that temperature is the dominant factor controlling strength development. A 10◦C increase in curing temperature resulted in a 40–60% increase in UCS, whereas variations in the alkali activator ratio produced only a 15–20% increase. The highest strength amplification, reaching 16 times that of untreated soil, was achieved using Ratio B at 60◦C, while Ratio A showed strength stagnation above 50◦C. Microstructural observations suggest that elevated temperatures accelerate geopolymer gel formation, leading to higher initial stiffness and an expanded elastic region. However, this also resulted in more brittle behavior, characterized by a higher brittleness index and rapid post-peak damage propagation for Ratio B, whereas Ratio A exhibited greater ductility. Overall, higher curing temperatures increased the dissipated energy at failure and revealed a clear strength–ductility trade-off. These findings provide insights for optimizing geopolymer stabilization of clay shale, particularly for geotechnical applications in tropical environments where elevated in situ temperatures are common.

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Published

2026-04-18

How to Cite

Diana, W., Hartono, E., Muntohar, A. S. ., & Abiyoga, N. P. . (2026). Unconfined Compressive Strength and Damage Evolution in Geopolymer-Stabilized Clay Shale: Role of Temperature and Alkali Activator Ratio. Journal of the Civil Engineering Forum, 12(2), 255–266. https://doi.org/10.22146/jcef.22477

Issue

Vol. 12 No. 2 (May 2026)

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