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Characterization of geopolymers from compositionally and physically different Class F fly ashes
Abstract The alkali-activation technology of coal fly ash is one of several potential solutions to minimize the harmful disposal of fly ash. This study reports high-resolution characterization of the alkali-activated reaction products for two representative Korean Class F fly ashes, which are significantly different in compositional and physical characteristics. The analysis confirms that differences in the network modifying element content, the amorphous phase content, and the particle size lead to large differences in compressive strength. Chabazite-Na and Al-rich chabazite-Na are identified as major crystalline phases in the high strength samples, supporting the favoring formation of ABC-6 family of zeolitic precursors for the higher mechanical strength while the C–S–H formation from the high CaO content (or crystalline CaO) is not a major source of the strength. The XRD analysis shows that the presence of amorphous humps located at 27–29° 2θ is not a sufficient indicator of geopolymeric gel formation. In the 29Si MAS NMR, some portion of −108ppm Q 4(0Al) peak is not related to quartz, implying that this portion of Si atoms actively participate in geopolymerization. The 27Al MAS NMR spectra exhibit more conversion of Al(V) and Al(VI) aluminum atoms into Al(IV) units in the higher strength sample, which can be an indication of more geopolymeric reaction.
Characterization of geopolymers from compositionally and physically different Class F fly ashes
Abstract The alkali-activation technology of coal fly ash is one of several potential solutions to minimize the harmful disposal of fly ash. This study reports high-resolution characterization of the alkali-activated reaction products for two representative Korean Class F fly ashes, which are significantly different in compositional and physical characteristics. The analysis confirms that differences in the network modifying element content, the amorphous phase content, and the particle size lead to large differences in compressive strength. Chabazite-Na and Al-rich chabazite-Na are identified as major crystalline phases in the high strength samples, supporting the favoring formation of ABC-6 family of zeolitic precursors for the higher mechanical strength while the C–S–H formation from the high CaO content (or crystalline CaO) is not a major source of the strength. The XRD analysis shows that the presence of amorphous humps located at 27–29° 2θ is not a sufficient indicator of geopolymeric gel formation. In the 29Si MAS NMR, some portion of −108ppm Q 4(0Al) peak is not related to quartz, implying that this portion of Si atoms actively participate in geopolymerization. The 27Al MAS NMR spectra exhibit more conversion of Al(V) and Al(VI) aluminum atoms into Al(IV) units in the higher strength sample, which can be an indication of more geopolymeric reaction.
Characterization of geopolymers from compositionally and physically different Class F fly ashes
Oh, Jae Eun (author) / Jun, Yubin (author) / Jeong, Yeonung (author)
Cement and Concrete Composites ; 50 ; 16-26
2013-10-20
11 pages
Article (Journal)
Electronic Resource
English
Characterization of geopolymers from compositionally and physically different Class F fly ashes
| Online Contents | 2014
Characterization of various fly ashes for preparation of geopolymers with advanced applications
| British Library Online Contents | 2013
| British Library Online Contents | 2014
| British Library Online Contents | 2014