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Coal gasification and composite ashes as partial replacements for Portland cement in concrete – strength and selected durability performance

Published online by Cambridge University Press:  16 November 2020

Mike Otieno Open the ORCID record for Mike Otieno [Opens in a new window]  and
Dikeledi Maboea
Mike Otieno*
Affiliation:
School of Civil and Environmental Engineering, University of the Witwatersrand, Johannesburg
Dikeledi Maboea
Affiliation:
School of Civil and Environmental Engineering, University of the Witwatersrand, Johannesburg
*
Corresponding author: Mike Otieno ([email protected])
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Abstract

This study investigated the use of mixed weathered coal fine ash (MWA) and coal gasification ash (CGA), sourced from Sasol® Ltd, South Africa, as partial replacements (10%, 15% and 30% by mass) of Portland Cement (PC) in concrete. The objective was to assess the feasibility of using the ashes, which are generally of lower quality than FA, in concrete in order to avert their negative environmental impact i.e. disposal in heaps and landfills. Companion reference concretes were made using conventional fly ash (FA). Two water-to-binder (w/b) ratios (0.50 and 0.60) were used. The concretes were tested for compressive strength (7, 28 and 56 days) and durability (gas permeability and chloride resistance at 28 and 56 days). In general, the results strongly suggest that the ashes can be used in conventional structural concrete – both from strength and durability viewpoints. Aspects that require attention when they are used include decrease in both workability and rate of strength gain. The gas permeability of the CGA and MWA concretes were similar to those for FA at all replacement levels but a 15% replacement level gave higher chloride resistance.

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Articles
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MRS Advances , Volume 5 , Issue 54-55: Nanoscale and Quantum Materials , 2020 , pp. 2807 - 2816
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Copyright
Copyright © The Author(s), 2020, published on behalf of Materials Research Society by Cambridge University Press

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References

Casper, J. K. P. (2010) Changing ecosystems: effects of global warming. Facts On File, Inc., New York, ISBN 978-1-4381-2739-2.Google Scholar
Grieve, G. (2009) Cementitious materials. Chapter 1, Fulton's Concrete Technology, Published by Erstwhile Cement and Concrete Institute, Midrand, South Africa, ISBN 978-0-9584779-1-8, pp. 1–16.Google Scholar
Ginster, M., Ratale, H. & Matjie, R. H. (2005) Beneficial utilisation of sasol coal gasification ash. Proceedings of the World of Coal Ash (WOCA), 11–15 April, 2005, Lexington, Kentucky, USA.Google Scholar
Venter, E. (2005) Sasol-Lurgi coal gasification technology and low rank coal. shorturl.at/drvyD, Available online (accessed on 4th April, 2020).Google Scholar
Matjie, R. H., Ginster, M., Alphen, C. V. & Sobiecki, A. (2005) Detailed characterisation of sasol ashes. Proceedings of the World of Coal Ash (WOCA), 11–15 April, 2005, Lexington, Kentucky, USA.Google Scholar
Mahlaba, J. S., Kearsley, E. P. & Kruger, R. A. (2011) Physical, chemical and mineralogical characterisation of hydraulically disposed fine coal ash from SASOL synfuels. Fuel, Vol. 90(7), pp. 2491–2500.CrossRefGoogle Scholar
ASTM-C-618 (2017) Standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete. ASTM International, 100 Barr Harbour Drive, West Conshohocken, PA 19428-2959, USA.Google Scholar
SANS-5862-1 (2006) Concrete tests: consistence of freshly mixed concrete - slump test. South African Standard Code of practice.Google Scholar
Mehta, P. K. & Monteiro, P. J. M. (2006) Concrete – microstructure, properties and materials, 3rd Edition. McGraw Hill, New York.Google Scholar
SANS-5863 (1994) Concrete tests - compressive strength of hardened concrete, Pretoria: South African Bureau of Standards.Google Scholar
SANS-3001-CO3-1 (2015) Civil engineering test methods: Part CO3-1: Concrete durability index testing - Preparation of test specimens. South African Bureau of Standards - Standards Division, Pretoria, South Africa, ISBN 978-0-626-32799-6.Google Scholar
SANS-3001-CO3-2 (2015) Civil engineering test methods: Part CO3-2: Concrete durability index testing - Oxygen permeability test. South African Bureau of Standards - Standards Division, Pretoria, South Africa, ISBN 978-0-626-32800-9.Google Scholar
SANS-3001-CO3-3 (2015) Civil engineering test methods: Part CO3-3: Concrete durability index testing - Chloride conductivity test. South African Bureau of Standards - Standards Division, Pretoria, South Africa, ISBN 978-0-626-32801-6.Google Scholar
Addis, B. & Goodman, J. (2009) Concrete mix design. Fulton's Concrete technology, 9th Edition (Chapter 11). Midrand, South Africa, Erstwhile Cement and Concrete Institute, pp. 219-228.Google Scholar
Neville, A. M. (2011) Properties of Concrete (5th Edition). Pearson Education Limited, Edinburg Gate, Harlow, Essex CM20 2JE, England, ISBN: 978-0-273-75580-7.Google Scholar
Wiens, U. & Schiessl, P. (1997) Chloride binding of cement paste containing fly ash. Proceedings of the 10th International Congress on the Chemistry of Cement (ICCC), 2-6 June, 1997, Goteborg, Sweden, Editor: Justnes, H., pp. 4–10.Google Scholar