The reactivity of fly ash in geopolymer synthesis: a qualification study by FTIR

Zhang, Z. and Wang, H. and Provis, J. L. (2012) The reactivity of fly ash in geopolymer synthesis: a qualification study by FTIR. In: 8th Asian-Australasian Conference on Composite Materials (ACCM 8): Enabling Tomorrow's Industry Today , 6-8 Nov 2012, Kuala Lumpur, Malaysia.

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Geopolymers are a family of green cementitious materials synthesized by alkali activation of aluminosilicate precursors. The chemical composition (mainly Al and Si) and high amorphous content enables fly ash to be one of the most suitable candidate raw materials for geopolymer synthesis. However, the reactivity of fly ash varies from source to source, and even from time to time at the same power station. Therefore, analysis of the reactivity of fly ash becomes an essential work for the wide manufacturing and application of geopolymers. In this study, FTIR spectroscopy was applied to analyse the environments of Al-O and Si-O bonds in fly ash. Five fly ashes from different sources were activated with a sodium silicate activator. Compressive strength testing showed no clear relationship with the overall Si/Al ratio or the content of amorphous phases in fly ash. By comparing the FTIR spectra, it is noted that the relative intensities of the bands at around 1000, 910 and 700 cm-1are much higher in fly ash with higher reactivity. These three band locations are respectively assigned to the asymmetric stretching of (Si, Al)-O-Si, the stretching of Si-O- units and symmetric stretching of Al-O in isolated [AlO4], in accordance with the understanding of silicate glass chemistry. Deconvolution analysis of the band from 400 to 1400 cm-1shows that the cumulative area of these three resolved bands, together with the band at ~1090 cm-1, the asymmetric stretching of Si(Al)-O-Si, is proportional to the reactivity of fly ash, which strongly suggesting that these three bonds are more reactive. If it is assumed that the area of the resolved bands is proportional to the concentration of the corresponding bonds, a general indication is therefore that fly ash containing more reactive bonds will exhibit higher reactivity in geopolymer synthesis. FTIR spectroscopy provides a fast and reliable approach to predict the reactivity of fly ash, from the perspective of glass chemistry.

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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Additional Information: Copyright © 2012 Asian-Australasian Association for Composite Materials (AACM). No parts of this document may be reproduced, stored in a retrieval system or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the permission of the copyright owner. Any request to reproduce any part of the proceedings should be directed to the publisher.
Faculty/School / Institute/Centre: Historic - Faculty of Engineering and Surveying - Department of Mechanical and Mechatronic Engineering
Date Deposited: 08 May 2013 04:41
Last Modified: 10 Nov 2014 23:53
Uncontrolled Keywords: geopolymer; fly ash; FTIR; reactivity; glass chemistry
Fields of Research : 09 Engineering > 0905 Civil Engineering > 090503 Construction Materials
03 Chemical Sciences > 0306 Physical Chemistry (incl. Structural) > 030606 Structural Chemistry and Spectroscopy
09 Engineering > 0912 Materials Engineering > 091201 Ceramics
Socio-Economic Objective: B Economic Development > 86 Manufacturing > 8610 Ceramics, Glass and Industrial Mineral Products > 861099 Ceramics, Glass and Industrial Mineral Products not elsewhere classified

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