The transition of fly ash-based geopolymer gels into ordered structures and the effect on the compressive strength

Ma, Xue and Zhang, Zuhua and Wang, Aiguo (2016) The transition of fly ash-based geopolymer gels into ordered structures and the effect on the compressive strength. Construction and Building Materials, 104. pp. 25-33. ISSN 0950-0618


This paper reports the investigation of microstructural properties associated with the transition of amorphous gels into more ordered structures in fly ash-based geopolymers. Three typical geopolymer mixes are synthesized with Class F fly ash and slag. Accelerated ageing scheme is performed at the 80 °C hydrothermal conditions, lasting for 90 days. It is observed that under the hydrothermal conditions, the two geopolymer pastes containing solely fly ash activated with sodium hydroxide and sodium silicate exhibit exhibit a common tendency to partial crystallization after 28 days. Crystalline zeolitic phases (including analcime) are detected by XRD and FTIR techniques. The SEM observation shows that the transition from the amorphous gels into more ordered structures takes place in the binder matrix randomly, rather than in pores or from particular structures. The blending of slag can reduce the transition (crystallization) trend, which is attributed to the formation of calcium containing gels. The decrease of compressive strength of geopolymer at late ageing stage can be correlated to the phase transition. Proper molecular designs of geopolymers to kinetically control the transition must be considered for the applications of this family of materials.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version cannot be displayed due to copyright restrictions.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering
Date Deposited: 03 Apr 2017 06:19
Last Modified: 03 Apr 2017 23:23
Uncontrolled Keywords: alkali activated cement; fly ash; slag; efflorescence; pore structure; cement; crystallization; durability; fly ash; geopolymer; phase; zeolite
Fields of Research : 09 Engineering > 0912 Materials Engineering > 091299 Materials Engineering not elsewhere classified
09 Engineering > 0905 Civil Engineering > 090503 Construction Materials
Socio-Economic Objective: B Economic Development > 87 Construction > 8703 Construction Materials Performance and Processes > 870301 Cement and Concrete Materials
Funding Details:
Identification Number or DOI: 10.1016/j.conbuildmat.2015.12.049

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