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)

Type
Article

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

KAUST Grant Number
KUS-l1-004021

Date
2012-05

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.

Citation
Oh JE, Moon J, Oh S-G, Clark SM, Monteiro PJM (2012) 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). Cement and Concrete Research 42: 673–685. Available: http://dx.doi.org/10.1016/j.cemconres.2012.02.002.

Acknowledgements
This publication was based on the work supported in part by Award no. KUS-l1-004021, made by King Abdullah University of Science and Technology (KAUST) and by NIST Grant no. 60NANB10D014. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract no. DE-AC02-05CH11231.

Publisher
Elsevier BV

Journal
Cement and Concrete Research

DOI
10.1016/j.cemconres.2012.02.002

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