Investigating Gel Molecular Structure and Its Relation with Mechanical Strength in Geopolymer Cement Based on Natural Pozzolan Using In Situ ATR-FTIR Spectroscopy
Publication: Journal of Materials in Civil Engineering
Volume 29, Issue 8
Abstract
In situ attenuated total-reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to investigate the gel formation of a natural pozzolan-based geopolymer and its relation to mechanical strength. For this purpose, geopolymer samples were prepared with different concentrations of (Si/Na) and (Na/Al) molar ratios in an alkali activator. The in situ ATR-FTIR showed that Si─O─T (T=Si, Al) stretching bond shifted to lower wave numbers with any increase in Si/Na molar ratio because of an increase in the geopolymerization reaction rate. The key finding of the present work is the relation between changes in gel molecular structure and the strength results demonstrated in different Si/Na and Na/Al molar ratios. Results showed that in high Na/Al and Si/Na molar ratios, Si─O─T bonds are formed at a lower wave number due to the presence of more Si─O species and increasing Al substitution in the silicate network of the geopolymer, which led to higher compressive strength.
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Acknowledgments
The authors thank Professor John L. Provis (Professor at the University of Sheffield) as supervisor of the first author in his Ph.D. program when he was at the University of Melbourne and for his valuable comments and useful discussions and assistance with FTIR spectroscopy and other data processing.
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Published In
Journal of Materials in Civil Engineering
Volume 29 • Issue 8 • August 2017
Copyright
©2017 American Society of Civil Engineers.
History
Received: Jun 23, 2016
Accepted: Dec 14, 2016
Published online: Apr 7, 2017
Published in print: Aug 1, 2017
Discussion open until: Sep 7, 2017
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