Quantitative Correlation between the Degree of Reaction and Compressive Strength of Metakaolin-Based Geopolymers

For geopolymers (usually composed of unreacted precursor and gel), the compressive strength is controlled by two factors. The first is the degree of reaction, or, equivalently, the amount of gel formed, including any calcium silicate hydrate gel in calcium-containing mixtures. The second factor is t...

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Bibliographic Details
Published in:Materials 2020-12, Vol.13 (24), p.5784
Main Authors: Chen, Xu, Kim, Eric, Suraneni, Prannoy, Struble, Leslie
Format: Article
Language:English
Subjects:
Aluminum
Calcium silicate hydrate
Calcium silicates
Cement
Composition
Compressive strength
Correlation analysis
Curing
Geopolymers
Humidity
Metakaolin
NMR
Nuclear magnetic resonance
Silicon
Spectrum analysis
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Summary:For geopolymers (usually composed of unreacted precursor and gel), the compressive strength is controlled by two factors. The first is the degree of reaction, or, equivalently, the amount of gel formed, including any calcium silicate hydrate gel in calcium-containing mixtures. The second factor is the gel composition, generally given by the Si/Al ratio. These two parameters are interrelated for typical silicate-activated metakaolin geopolymers. By separating out effects of Si/Al ratio and degree of reaction, this study quantitatively correlates the degree of reaction with the compressive strength of metakaolin-based geopolymers with and without calcium. Solid-state Si nuclear magnetic resonance (NMR) aided with chemical extractions was used to determine gel amounts and composition for several geopolymer mixtures. The compressive strength was also measured for each mixture at 7 days. Both the increase of Na/Al ratio in mixtures without calcium and addition of external calcium increased the degree of reaction, and compressive strength correlated linearly (R > 0.88) with the degree of reaction.
ISSN:1996-1944
1996-1944
DOI:10.3390/ma13245784