Effect of fly ash and metakaolin on the macroscopic and microscopic characterizations of magnesium oxychloride cement

Gong, Wei; Wang, Nan; Zhang, Na

doi:10.1016/j.conbuildmat.2020.120957

Cited by 26 publications

(16 citation statements)

References 31 publications

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“…Interestingly, both initial and final setting time decreases as the dosage of FA increases in the mixtures, attributing to the decreased available free water in the fresh mixture. Such a prolonged effect of the setting process was also reported by Chau and Gong, which showed a delay time of 1–4 h [ 9 , 30 ].…”

Section: Role Of Fly Ash In Moc Pastessupporting

confidence: 69%

“…However, as FA further added, a larger expansion ratio was observed by the strip gauge tests, indicating looser microstructure and wider gaps [ 35 ]. According to related expansion specifications (0.3% at 28d as per GB/T 33544) [ 9 ], the maximum dosage of FA in MOC pastes is limited below 30 wt. %, with an expansion ratio of 0.298% at 28 d.…”

Section: Role Of Fly Ash In Moc Pastesmentioning

confidence: 99%

“…MOC, produced from magnesium oxide and magnesium chloride mainly, is commonly used in various building materials, such as fire-resistant panels, tiles, decorative components, ventilation pipes, etc. [ 9 , 10 ]. Compared with traditional cement, MOC has the advantages of ultra-high strength, wear and fire resistance.…”

Section: Introductionmentioning

confidence: 99%

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Eco-Sustainable Magnesium Oxychloride Cement Pastes Containing Waste Ammonia Soda Residue and Fly Ash

et al. 2022

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Magnesium oxychloride cement (MOC), a type of special construction material, has drawn much research attention in solid waste utilization and environmental protection due to its eco-friendly production. Ammonia soda residue (ASR), a by-product generated from sodium carbonate manufacturing, is one of the industrial wastes that can be recycled in MOC systems. However, ASR exhibits adverse effects on the fresh performance and volume stability of MOC pastes. This paper aims at improving the properties of ASR-MOC by introducing fly ash (FA), solid waste from the power industry. Firstly, the roles of FA in MOC pastes are evaluated and analyzed. Then, three substitution ratios of FA (33.3%, 50% and 66.7% in weight) for ASR are designed for MOC pastes with 10% to 40% industrial wastes. Flowability, setting, strength and expansion of all mixtures were experimentally studied. Furthermore, X-ray diffraction (XRD) and scanning electron microscope (SEM) approaches were adopted to illustrate the microstructure changes. Results show that by adding different amounts of FA, the inferior flowability of MOC caused by ASR can be improved by 6–23%, the setting process can be prolonged by 30–55% and the expansion ratio can be reduced by 14–66%. The intensity of characteristic peaks of 5-phase and Mg(OH)2, together with the degrees of crystallization in XRD curves, well explain the strength variation and volume stability of ASR-MOC pastes. According to the regulation of relative specification, up to 20% of solid wastes in weight (10% FA + 10% ASR) can be consumed, contributing greatly to the greener sustainable development of construction materials.

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Section: Role Of Fly Ash In Moc Pastessupporting

confidence: 69%

Section: Role Of Fly Ash In Moc Pastesmentioning

confidence: 99%

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Eco-Sustainable Magnesium Oxychloride Cement Pastes Containing Waste Ammonia Soda Residue and Fly Ash

et al. 2022

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“…The flexural strength, compressive strength, dynamic modulus of elasticity and water absorption coefficient data is presented in Table 6 . The reference composite with silica aggregate exhibited high mechanical resistance and stiffness such typical for MOC-based materials [ 68 , 69 ]. The mechanical strength and stiffness corresponded to their high porosity, i.e., these parameters were greatly reduced in comparison with the control material MOC-Sref.…”

Section: Resultsmentioning

confidence: 99%

Foam Glass Lightened Sorel’s Cement Composites Doped with Coal Fly Ash

et al. 2021

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Lightweight Sorel’s cement composites doped with coal fly ash were produced and tested. Commercially available foam granulate was used as lightening aggregate. For comparison, reference composites made of magnesium oxychloride cement (MOC) and quartz sand were tested as well. The performed experiments included X-ray diffraction, X-ray fluorescence, scanning electron microscopy, light microscopy, and energy dispersive spectroscopy analyses. The macro- and microstructural parameters, mechanical resistance, stiffness, hygric, and thermal parameters of the 28-days matured composites were also researched. The combined use of foam glass and fly ash enabled to get a material of low weight, high porosity, sufficient strength and stiffness, low water imbibition, and greatly improved thermal insulation performance. The developed lightweight composites can be considered as further step in the design and production of alternative and sustainable materials for construction industry.

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“…Furthermore, adding MK can significantly improve the mechanical properties and freeze-thaw durability of traditional Portland cement [18]. Incorporating MK into MOC had been reported in terms of macroperformance such as a quantitative analysis of changes in quality and compactness and mechanical properties, as well as in terms of microstructure, such as an analysis of the phase composition of hydration products and microscopic morphology [19]. Integrating MK into magnesium phosphate cement (MPC) improved the 28 day compressive and tensile bonding strength of cement mortar, as well as the frost resistance and water resistance, while it reduced the drying shrinkage [20].…”

Section: Introductionmentioning

confidence: 99%

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

Liu

et al. 2022

Materials

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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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Effect of fly ash and metakaolin on the macroscopic and microscopic characterizations of magnesium oxychloride cement

Cited by 26 publications

References 31 publications

Eco-Sustainable Magnesium Oxychloride Cement Pastes Containing Waste Ammonia Soda Residue and Fly Ash

Eco-Sustainable Magnesium Oxychloride Cement Pastes Containing Waste Ammonia Soda Residue and Fly Ash

Foam Glass Lightened Sorel’s Cement Composites Doped with Coal Fly Ash

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

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