Microstructural and compositional change of NaOH-activated high calcium fly ash by incorporating Na-aluminate and co-existence of geopolymeric gel and C–S–H(I)

Jae Eun Oh, Juhyuk Moon, Sang-Gyun Oh, Simon M. Clark, Paulo J. M. Monteiro

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

This study explores the reaction products of alkali-activated Class C fly ash-based aluminosilicate samples by means of high-resolution synchrotron X-ray diffraction (HSXRD), scanning electron microscope (SEM), and compressive strength tests to investigate how the readily available aluminum affects the reaction. Class C fly ash-based aluminosilicate raw materials were prepared by incorporating Na-aluminate into the original fly ashes, then alkali-activated by 10 M NaOH solution. Incorporating Na-aluminate reduced the compressive strength of samples, with the reduction magnitude relatively constant regardless of length of curing period. The HSXRD provides evidence of the co-existence of C-S-H with geopolymeric gels and strongly suggests that the C-S-H formed in the current system is C-S-H(I). The back-scattered electron images suggest that the C-S-H(I) phase exists as small grains in a finely intermixed form with geopolymeric gels. Despite providing extra source of aluminum, adding Na-aluminate to the mixes did not decrease the Si/Al ratio of the geopolymeric gel. © 2012 Elsevier Ltd.
Original languageEnglish (US)
Pages (from-to)673-685
Number of pages13
JournalCement and Concrete Research
Volume42
Issue number5
DOIs
StatePublished - May 2012
Externally publishedYes

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