Including Class F Fly Ash to Improve the Geopolymerization Effects and the Compressive Strength of Mine Tailings-Based Geopolymer

Nan Zhang, Ahmadreza Hedayat, Yibran Perera-Mercado, Héctor Gelber Bolaños Sosa, Néstor Tupa, Isaac Yanqui Morales, Reynaldo Sabino Canahua Loza

Research output: Contribution to journalArticlepeer-review


Mine tailings (MTs) that are rich in aluminosilicates can be reused to create geopolymer via alkaline activation as an alternative to portland cement concrete for construction and building applications. However, pure MTs may lack sufficient aluminum or amorphous aluminosilicates to facilitate geopolymerization that competes with traditional concrete. It is essential, therefore, to add supplemental aluminum source materials and amorphous aluminosilicates to adjust the Si Al ratio to change the geopolymeric cell structures of MTs. The study presented in this paper utilized Class F fly ash (FA) as the amorphous supplement for better reactivity or aluminum source to alter the Si Al ratio that can be reacted through alkali activation to facilitate better geopolymerization. First, a series of laboratory tests was conducted to obtain the characterizations of the FA. Then geopolymer samples using different amounts of FA were produced by activating the MTs+FA mixtures with 10 M NaOH solutions at a moisture ratio of 16% cured for 7 days with a slightly elevated temperature. Finally, uniaxial compression tests (UCTs) were applied to evaluate the influence of the addition of different amounts of FA (5%, 10%, 15%, and 20%) on the compressive behaviors. In addition, microscopic insights with different FA additions were evaluated regarding morphology, chemical bonds, and mineralogy. Results show that adding FA supplements based on the initial moisture content and curing conditions increased the mechanical behavior of the geopolymer specimens, followed by a decrease due to insufficient water for a chemical reaction. However, due to the water loss during the curing process, improvement in mechanical properties began to decrease when the FA was increased to 20%.

Original languageEnglish
Article number04022313
JournalJournal of Materials in Civil Engineering
Issue number11
StatePublished - 1 Nov 2022

Bibliographical note

Funding Information:
We acknowledge the financial support provided for this work by the Universidad Nacional de San Agustín (UNSA) through the joint Center for Mining Sustainability with the Colorado School of Mines.

Publisher Copyright:
© 2022 American Society of Civil Engineers.


  • Admixture
  • Fly ash (FA)
  • Geopolymer
  • Mine tailings (MTs)
  • Uniaxial compression test


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