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Effect of Fly Ash and Metakaolin on Properties and Microstructure of Magnesium Oxysulfate Cement

To improve the mechanical performance and lower the production cost of magnesium oxysulfate cement (MOSC), this article investigates the effects of single and compounded addition of metakaolin (MK) and/or fly ash (FA) on the setting time, mechanical strength, water resistance, hydration product, com...

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Autores principales: Liu, Tong, Li, Chunqing, Li, Li, Fan, Wenqiang, Dong, Yudong, Liang, Huihui, Yang, Hongjian
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8874730/
https://www.ncbi.nlm.nih.gov/pubmed/35207882
http://dx.doi.org/10.3390/ma15041334
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author Liu, Tong
Li, Chunqing
Li, Li
Fan, Wenqiang
Dong, Yudong
Liang, Huihui
Yang, Hongjian
author_facet Liu, Tong
Li, Chunqing
Li, Li
Fan, Wenqiang
Dong, Yudong
Liang, Huihui
Yang, Hongjian
author_sort Liu, Tong
collection PubMed
description To improve the mechanical performance and lower the production cost of magnesium oxysulfate cement (MOSC), this article investigates the effects of single and compounded addition of metakaolin (MK) and/or fly ash (FA) on the setting time, mechanical strength, water resistance, hydration product, composition, and microstructure of the resulting cement. MOSC samples with different proportions, ranging from 0 to 30 wt.%, of FA and/or MK substituting magnesium oxide (MgO) were prepared. The microstructure was explored by scanning electron microscopy, X-ray diffraction, and mercury intrusion porosimetry. The findings suggest that adding FA can delay the setting of MOSC; however, the effect of adding MK to MOSC was reversed. Furthermore, the phase composition of the MOSC hydration products was unaltered upon adding FA and/or MK, but thicker and longer 517 phase crystals were observed. FA and MK can effectively fill the large pores of MOSC through filling and nucleation effects, reduce the pore size, and form a denser microstructure, thereby improving its mechanical properties. The optimal MOSC sample was found by substituting 10 wt.% of both FA and MK, resulting in a cement that exhibited a short setting time and an incredibly high mechanical strength and density. These findings will further the development of stronger, more cost-efficient, and more water-resistant MOSC products.
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spelling pubmed-88747302022-02-26 Effect of Fly Ash and Metakaolin on Properties and Microstructure of Magnesium Oxysulfate Cement Liu, Tong Li, Chunqing Li, Li Fan, Wenqiang Dong, Yudong Liang, Huihui Yang, Hongjian Materials (Basel) Article To improve the mechanical performance and lower the production cost of magnesium oxysulfate cement (MOSC), this article investigates the effects of single and compounded addition of metakaolin (MK) and/or fly ash (FA) on the setting time, mechanical strength, water resistance, hydration product, composition, and microstructure of the resulting cement. MOSC samples with different proportions, ranging from 0 to 30 wt.%, of FA and/or MK substituting magnesium oxide (MgO) were prepared. The microstructure was explored by scanning electron microscopy, X-ray diffraction, and mercury intrusion porosimetry. The findings suggest that adding FA can delay the setting of MOSC; however, the effect of adding MK to MOSC was reversed. Furthermore, the phase composition of the MOSC hydration products was unaltered upon adding FA and/or MK, but thicker and longer 517 phase crystals were observed. FA and MK can effectively fill the large pores of MOSC through filling and nucleation effects, reduce the pore size, and form a denser microstructure, thereby improving its mechanical properties. The optimal MOSC sample was found by substituting 10 wt.% of both FA and MK, resulting in a cement that exhibited a short setting time and an incredibly high mechanical strength and density. These findings will further the development of stronger, more cost-efficient, and more water-resistant MOSC products. MDPI 2022-02-11 /pmc/articles/PMC8874730/ /pubmed/35207882 http://dx.doi.org/10.3390/ma15041334 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Liu, Tong
Li, Chunqing
Li, Li
Fan, Wenqiang
Dong, Yudong
Liang, Huihui
Yang, Hongjian
Effect of Fly Ash and Metakaolin on Properties and Microstructure of Magnesium Oxysulfate Cement
title Effect of Fly Ash and Metakaolin on Properties and Microstructure of Magnesium Oxysulfate Cement
title_full Effect of Fly Ash and Metakaolin on Properties and Microstructure of Magnesium Oxysulfate Cement
title_fullStr Effect of Fly Ash and Metakaolin on Properties and Microstructure of Magnesium Oxysulfate Cement
title_full_unstemmed Effect of Fly Ash and Metakaolin on Properties and Microstructure of Magnesium Oxysulfate Cement
title_short Effect of Fly Ash and Metakaolin on Properties and Microstructure of Magnesium Oxysulfate Cement
title_sort effect of fly ash and metakaolin on properties and microstructure of magnesium oxysulfate cement
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8874730/
https://www.ncbi.nlm.nih.gov/pubmed/35207882
http://dx.doi.org/10.3390/ma15041334
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