RESEARCH ARTICLE
Utilization of Circulating Fluidized Bed Fly Ash as Pozzolanic Material
Kae- Long Lin1, *, Ta-Wui Cheng2, Chih-Hsuan Ho3, Yu-Min Chang4, Kang-Wei Lo2
Article Information
Identifiers and Pagination:
Year: 2017Volume: 11
First Page: 176
Last Page: 186
Publisher ID: TOCIEJ-11-176
DOI: 10.2174/1874149501711010176
Article History:
Received Date: 26/9/2016Revision Received Date: 17/11/2016
Acceptance Date: 19/12/2016
Electronic publication date: 24/02/2017
Collection year: 2017
open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Abstract
A circulating fluidized bed (CFB) boiler generates energy by burning petroleum coke. Because burnt petroleum coke has a high sulfur content, limestone is added to the boiler to reduce the emittance of sulfur dioxide through desulfuration. The residue collected from the boiler is called CFB ash. CFB boilers in Taiwan can produce 328,000 tonnes of CFB fly ash per year. In this study, the pozzolanic characteristics of CFB fly ash were investigated by blending CFB fly ash and ordinary Portland cement (OPC). The CFB fly ash was mainly composed of CaO, SO3, and SiO2 in concentrations of 37.8%, 9.2%, and 2.2%, respectively. The crystals of CFB fly ash contained 3CaO.SiO2, 2CaO.SiO2, Ca(OH)2, C-S-H (Tobermolite), and Ettringite. The results revealed that applying the toxicity characteristic leaching procedure to CFB fly ash renders it suitable for use in blended cement. At later curing ages (90 days), the pore volumes of both the OPC and the CFB-fly-ash-blended cement pastes (CFBFABCP) decreased as the curing time increased. A possible explanation is that C3S and C2S were consumed to form C-S-H gel, resulting in an increase in the Q1 and Q2 groups identified by 29Si Nuclear Magnetic Resonance (NMR) spectroscopy. Furthermore, the peak of the Q0 group decreased, but those of the Q1 and Q2 peaks increased with an increasing curing time. The pozzolanic activity of the CFBFABCP containing 10% CFB fly ash indicates that it is a suitable substitute for OPC in blended cement.
