A sustainable landfill liner material: clay-fly ash geopolymers

• Published in: Bulletin of engineering geology and the environment Vol. 80; no. 5; pp. 4111 - 4124
• Main Authors: Khaksar Najafi, Elmira, Jamshidi Chenari, Reza, Payan, Meghdad, Arabani, Mahyar
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2021
• Subjects: Earth and Environmental Science; Earth Sciences; Foundations; Geoecology/Natural Processes; Geoengineering; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Nature Conservation; Original Paper; Durability; Sorption capacity; Clay-fly ash geopolymers; Permeability; Landfill liner
• ISSN: 1435-9529; 1435-9537
• DOI: 10.1007/s10064-021-02185-7

Geopolymers offer a number of benefits, including high sorption capacity, sufficient durability, and substantial mechanical strength as well as low CO 2 emission and limited drying shrinkage, which may make them sustainable candidates to be utilized as landfill liner materials. Hence, this research is aimed at evaluating how a clay-fly ash geopolymer can meet the requirements proposed for mineral liners so as to compensate for the scarcity of suitable local clay. In this study, clay-fly ash geopolymers are synthesized from the mixtures containing 60% fly ash to the total solid mass and then activated by 10 M NaOH solutions. Several experiments are conducted to assess the mechanical strength, permeability, durability, and sorption capacity of the proposed liner material. Results depict that geopolymerzation has led to a prominent alteration in clay structure, contributing to a non-plastic soil with lower swelling potential and desiccation cracking probability. Proven to enhance sorption capacity and resist freeze-thaw cycles, the clay-fly ash geopolymers are shown to satisfy the criteria of volume shrinkage < 4%, permeability ≤ 1×10 −7 cm/s, unconfined compressive strength > 200 kPa, and plasticity index < 7–10. Microstructural analyses also corroborate that the binding agents result in the formation of coagulated particles covered by aluminosilicate gels, thus rendering a more sustainable material. Additionally, the sorption capacity of the clay-fly ash geopolymers exposed to freeze-thaw cycles also shows comparable values to the unexposed specimens.