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Materials 2015, 8(2), 784-798; doi:10.3390/ma8020784

Recycling of Sustainable Co-Firing Fly Ashes as an Alkali Activator for GGBS in Blended Cements

1
Institute of Materials Engineering, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung 20224, Taiwan
2
Taiwan & Pacific Engineers & Constructors Ltd., Taipei 10669, Taiwan
3
Department of Harbor and River Engineering, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung 20224, Taiwan
4
Department of Civil Engineering, National Ilan University, I-Lan 26047, Taiwan
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Academic Editor: Abdel Magid Hamouda
Received: 19 October 2014 / Revised: 12 January 2015 / Accepted: 11 February 2015 / Published: 16 February 2015
(This article belongs to the Section Advanced Composites)
View Full-Text   |   Download PDF [1788 KB, uploaded 16 February 2015]   |  

Abstract

This study investigates the feasibility of co-firing fly ashes from different boilers, circulating fluidized beds (CFB) or stokers as a sustainable material in alkali activators for ground granulated blast-furnace slag (GGBS). The mixture ratio of GGBS and co-firing fly ashes is 1:1 by weight. The results indicate that only CF fly ash of CFB boilers can effectively stimulate the potential characteristics of GGBS and provide strength as an alkali activator. CF fly ash consists of CaO3 (48.5%), SiO2 (21.1%), Al2O3 (13.8%), SO3 (10.06%), Fe2O3 (2.25%) and others (4.29%). SA fly ash consists of Al2O3 (19.7%), SiO2 (36.3%), Fe2O3 (28.4%) and others (15.6%). SB fly ash consists of Al2O3 (15%), SiO2 (25.4%), Zn (20.6%), SO3 (10.9%), Fe2O3 (8.78%) and others (19.32%). The mixtures of SA fly ash and SB fly ash with GGBS, respectively, were damaged in the compressive strength test during seven days of curing. However, the built up strength of the CF fly ash and GGBS mixture can only be maintained for 7–14 days, and the compressive strength achieves 70% of that of a controlled group (cement in hardening cement paste). The strength of blended CF fly ash and GGBS started to decrease after 28 days, and the phenomenon of ettrigite was investigated due to the high levels of sulfur content. The CaO content in sustainable co-firing fly ashes must be higher than a certain percentage in reacting GGBS to ensure the strength of blended cements. View Full-Text
Keywords: sustainable materials; co-firing fly ashes; GGBS; innovative alkali activators sustainable materials; co-firing fly ashes; GGBS; innovative alkali activators
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. (CC BY 4.0).

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MDPI and ACS Style

Wu, Y.-H.; Huang, R.; Tsai, C.-J.; Lin, W.-T. Recycling of Sustainable Co-Firing Fly Ashes as an Alkali Activator for GGBS in Blended Cements. Materials 2015, 8, 784-798.

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