期刊
CEMENT & CONCRETE COMPOSITES
卷 78, 期 -, 页码 21-32出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.cemconcomp.2016.12.010
关键词
Geopolymer; Metakaolin; Nanoindentation; Nanomechanical properties; Reaction kinetics
资金
- US National Science Foundation [CMMI-1301048, CMMI-1405745]
A multiscale study is presented of the reaction kinetics, phase formation, mechanical properties of metakaolin-based geopolymers by varying Si/Al ratios of 1.2-2.2 and Na/Al ratios of 0.6-1.2. Macro- and nano-mechanical properties of geopolymer samples were determined by unconfined compression testing and grid nanoindentation technique, respectively. The latter, in combination with statistical deconvolution, also enables the extraction of generally 4 distinct phases together with their nano mechanical properties and volumetric fraction within the synthesized geopolymers. Moreover, the reaction kinetics, phase formation (particularly geopolymer gel development), and mechanical property development were investigated by characterizing geopolymers cured at the final setting time, 7, and 28 days. Phase formation was characterized by Fourier transform infrared spectroscopy (FTIR) via monitoring the evolution of the Si-O-T (T: Si or Al) and Al-O bonds. Results illustrate that the fraction of geopolymer gels dominantly governs the mechanical behavior, both of which increase with the Si/Al and Na/Al molar ratios, while the final setting time increases with the Si/Al ratio, but decreases with the Na/Al ratio. The chemical composition for the best mechanical performance of the studied geopolymers is a Si/Al ratio of 1.7 and Na/Al ratio of 0.9. The relationships among geopolymer chemical compositions, geopolymer gel formation rate, and macromechanical properties are also discussed. (C) 2017 Elsevier Ltd. All rights reserved.
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