Effects of Curing Conditions and Sand-to-Binder Ratios on Compressive Strength Development of Fly Ash Geopolymer
Publication: Journal of Materials in Civil Engineering
Volume 30, Issue 2
Abstract
This paper investigates the effects of curing conditions on a high-strength geopolymer material synthesized by activating different combinations of Class F fly ash (FA), ground-granulated blast-furnace (slag), and ultrafine fly ash (UFFA) with a unified mixture of D-grade sodium silicate () and 12-M sodium hydroxide (NaOH) solutions. The effect of ambient air and water curing on the strength properties, cumulative porosity, and microstructure of geopolymer mortar samples was evaluated at room temperature. Subsequently, the effects of two different sand-binder ratios, the amount of FA replacement with UFFA, and slag on the short-term mechanical properties and workability of geopolymer mixtures is also discussed. The results show that the geopolymer specimens cured in water possessed a higher total porosity in relation to the air-cured samples. Air curing resulted in additional polymerization and fewer microcracks were observed within the scanning electron microscope photographs, which led to an increased compressive strength. Moreover, the use of UFFA was observed to significantly improve the strength of FA-slag blended geopolymers, where reduced porosity and denser microstructure in FA geopolymers was observed with the inclusion of slag at higher quantities.
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Acknowledgments
The authors are grateful for the research support provided by Australian Research Council under Grant DP160104557. The assistance provided by the concrete laboratory staff at Curtin University is duly appreciated. The authors also acknowledge the use of equipment and scientific and technical assistance of the Curtin University Electron Microscopy Facility, which has been partially funded by the university and state and commonwealth governments.
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Published In
Journal of Materials in Civil Engineering
Volume 30 • Issue 2 • February 2018
Copyright
©2017 American Society of Civil Engineers.
History
Received: Oct 20, 2016
Accepted: Jun 28, 2017
Published online: Nov 22, 2017
Published in print: Feb 1, 2018
Discussion open until: Apr 22, 2018
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