期刊
CEMENT & CONCRETE COMPOSITES
卷 57, 期 -, 页码 34-43出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.cemconcomp.2014.12.005
关键词
Fly ash; Geopolymer; Alkali; NMR spectroscopy; Pore structure; Microstructure
资金
- Schools of Engineering
- College of Liberal Arts and Sciences at Arizona State University (ASU)
The influence of alkali cation (M = Na or K) on the geopolymerization of fly ash is evaluated. NaOH, KOH (4 M and 8 M), or Na/K silicates (SiO2/M2O = 2.0) are used as the activators. Na-activated systems demonstrate higher strengths than the K-based ones after thermal activation, with the 8 M NaOH activation being the most efficient. The total pore volume fractions are comparable between the pastes activated using similar Na- or K-based activators, but the volume of pores of size >0.2 mu m is higher for the K-based systems, attributed to the reduced dissociation efficiency, faster condensation and reduced time for rearrangement. Compressive strength is shown to be closely related to the volume pores of size >0.2 mu m. The presence of soluble silicates from the activator significantly influences the pore size distribution. Si-29 MAS NMR spectroscopy reveals an increase in gel structural order and higher amounts of Si-rich units as the activator alkalinity increases, and a higher degree of disorder for the K-based systems. (C) 2014 Elsevier Ltd. All rights reserved.
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