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Advances in Materials Science and Engineering
Volume 2018 (2018), Article ID 1942898, 11 pages
Research Article

Synthesis and Characterization of Porous Fly Ash-Based Geopolymers Using Si as Foaming Agent

1National Technical University of Athens, School of Chemical Engineering, 9 Heroon Polytechniou St., 15773 Athens, Greece
2Hellenic Open University, School of Science and Technology, 18 Parodos Aristotelous St., 26335 Patras, Greece

Correspondence should be addressed to S. Tsivilis

Received 17 September 2017; Revised 13 November 2017; Accepted 15 November 2017; Published 28 January 2018

Academic Editor: Fernando Lusquiños

Copyright © 2018 D. Kioupis et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This paper concerns the synthesis of foamed geopolymers using fly ash and metallic Si as the binder and the porogent agent, respectively. The Taguchi approach was applied in order to study the effect of some significant synthesis parameters such as the Si foaming agent content (% w/w fly ash based), the alkali type (R : Na or K), and the alkalinity (R/Al molar ratio) of the activation solution on the compressive strength and apparent density of the foamed geopolymers. The final products were characterized by means of XRD, FTIR, and SEM, while optical microscopy was applied for the evaluation of the porosity. Lightweight geopolymers with a compressive strength of 2.08–14.88 ΜPa and an apparent density of 0.84–1.55 g/cm3 were prepared by introducing a Si content up to 0.2% w/w on fly ash basis.