Volume 93 Issue 1, Pages 272 – 278

Xiaolu Guo, Huisheng Shi, Warren Dick
Published Online: Oct 20 2009

DOI: 10.1111/j.1551-2916.2009.03331.x

Geopolymerization is a developing field that can
beneficially use heat-treated water treatment residuals (WTRs) to create
fly ash-based geopolymers. In this study, geopolymers made only from
fly ash (FA) and from FA plus calcined WTRs (FA–WTRs) were evaluated.
The proper calcining condition for WTRs is 900°C for 1 h and the optimum
amount of WTRs to mix with FA is 10 wt%. Compressive strength of
samples cured at 75°C for 24 h can reach 68.1 MPa, and when cured at
23°C for 28 days the values were >50 MPa. Further studies were
conducted on FA and FA–WTRs geopolymer samples cured at 75°C for 8 h
followed by 23°C for 28 d. X-ray diffraction patterns of geopolymers
made from FA indicate the presence of amorphous geopolymeric and calcium
silicate hydrate (C–S–H) gels, and a type of zoelite similar to
gismondine. When WTRs replaced some of the FA, amorphous geopolymeric
gels are mainly formed. Scanning electron micrographs indicate spherical
unreactivated FA and other particles are combined and surround the
geopolymeric and C–S–H gels. Utilization of WTRs in creation of FA-based
geopolymers can lead to a new type of cementitious binder.

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