Effects of Fly Ash and Hexadecyltrimethoxysilane on the Compressive Properties and Water Resistance of Magnesium Oxychloride Cement

Guan, Bowen; He, Zhenqing; Wei, Fulu; Wang, Faping; Yu, Jincheng

doi:10.3390/polym15010172

Cited by 5 publications

(5 citation statements)

References 26 publications

(43 reference statements)

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“…FA is a byproduct of the coal industry, and it was discovered that using FA considerably increased the water resistance of MOC. Figure 2 depicts the water resistance coefficients of FA-modified MOC composites as reported in previous studies [66,67]. Previous research has shown that incorporating 30% FA into MOC mortar (14 d air-cured) resulted in 80% compressive strength retention with respect to the initial value after 28 d of immersion in water [22,68].…”

Section: Influence Of Scms On the Properties Of Moc 41 Effect Of Fa O...mentioning

confidence: 74%

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Magnesium Oxychloride Cement: Development, Opportunities and Challenges

Ahmad,

Rawat,

Zhang

2024

Applied Sciences

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Magnesium oxychloride cement (MOC), an alternative to ordinary Portland cement (OPC), has attracted increasing research interest for its excellent mechanical properties and its green and sustainable attributes. The poor water resistance of MOC limited its usage mainly to indoor applications; nevertheless, recent advances in water-resistant MOC have expanded the material’s potential applications from indoor to outdoor. This review aims to showcase recent advances in MOC, including water-resistant MOC and ductile fiber-reinforced MOC (FRMOC), exploring their potential applications including in sustainable construction for future generations. The mechanism under different curing procedures such as normal and CO2 curing and the effect of different inorganic and organic additives on the water resistance of MOC composites are discussed. In particular, the review highlights the recent developments in achieving over 100% strength retention under water at 28 days as well as advancements in FRMOC, where tensile strength has surpassed 10 MPa with a remarkable strain capacity ranging from 4–8%. This paper also sheds light on the potential applications of MOC as a fire-resistant coating material, green-wood-MOC composite building material, and in reducing solid waste industrial byproduct accumulations. Finally, this study suggests future research directions to enhance the practical application of MOC.

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Section: Influence Of Scms On the Properties Of Moc 41 Effect Of Fa O...mentioning

confidence: 74%

“…Strength retention coefficient of FA-modified MOC after water immersion. (Note-CM: control mix, HDTMS: hexadecyltrimethoxysilane, and SF: silica fume)[19,20,22,66,68].…”

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confidence: 99%

Magnesium Oxychloride Cement: Development, Opportunities and Challenges

Ahmad,

Rawat,

Zhang

2024

Applied Sciences

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“…The dense microstructure of the MOC was primarily attributed to the filling effect of fine fly ash particles and the formation of Mg-Cl-Si-H gel. This increases the water resistance of the MOC-stabilized crushed stone to a certain extent 8,11,13,36,38 . However, when the fly ash content surpasses a certain proportion, the excessive fly ash increases the proportion of harmful pores, adversely affecting the water resistance.…”

Section: Experimental Results and Analysismentioning

confidence: 99%

Mixture composition design of magnesium oxychloride cement-stabilized crushed stone materials applied as a pavement base

Zhang,

Luo,

Sun

2024

Sci Rep

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Conventional binding materials, such as silicate cement and lime, present high energy consumption, pollution, and carbon emissions. Therefore, we utilize crushed stone as a stabilization material. Magnesium oxychloride cement (MOC) is modified and used as an inorganic admixture owing to its eco-friendly nature and low carbon content. We analysed the control indicators of an integrated design of MOC-stabilized crushed stone by conducting unconfined compressive strength and water-resistance tests. The optimum mixing composition of the MOC-stabilized crushed stone was determined through the response surface methodology. We determined the best approach and dosage for improving the water resistance of MOC-stabilized crushed stone by comparing the effects of four modification methods: fly ash, citric acid + silica fume, phosphoric acid + waterborne polyurethane, and dihydrogen phosphate potassium salt. We also perform a comparison with 5% ordinary silicate cement-stabilized crushed stone. The results indicate that the MOC-stabilized crushed stone exhibits a rapid increase in strength in the early stage, but this rate reduces after 28 days. The mixing design employs the 4-day unconfined compressive strength and 1-day water resistance coefficient as the technical indicators. The best mixing composition includes a 4.27% MOC dosage and a molar ratio of MgO/MgCl2 of 5.85. We use 1% citric acid + 10% silica fume in equal amounts to replace the MOC dopant method for composite modification of the MOC stabilized crushed stone. Consequently, the 1-day water resistance coefficient before water immersion is significantly increased from 0.78 to 0.91 and its 4-day unconfined compressive strength is only reduced by 0.10 MPa. This significantly improves the water resistance of the MOC-stabilized crushed stone and ensures that its strength remains unaffected, which is the optimal modification method. However, this method must ensure that a small amount of citric acid and silica fume are uniformly distributed in the MOC-stabilized crushed stone, which increases the construction difficulty of the road base.

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“…Solidification/stabilization (S/S) methods can prevent harmful chemicals from being released into the environment though chemical or mechanical binding using curing agents [6,[58][59][60]. Magnesium oxychloride cement (MOC), known as Sorel cement, comprises MgO and MgCl 2 ; it is typically used as a curing agent for S/S of solid waste, because of its good engineering and mechanical properties, fast curing, air hardening, good resistance to abrasion and fire, and so on [61][62][63][64][65][66][67]. MgO and MgCl 2 react with water to form MgO-MgCl 2 -H 2 O systems such as Mg(OH) 2 •MgCl 2 •8H 2 O (phase 3) and 5 Mg(OH) 2 •MgCl 2 •8H 2 O (phase 5), which are the main substances to form strength of MOC-solid waste in the solidifying process [64,[67][68][69][70][71][72][73][74][75].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties and Water Resistance of Magnesium Oxychloride Cement–Solidified Residual Sludge

Liang

Wang

et al. 2023

Processes

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As a solid waste, the amount of residual sludge produced by the municipal wastewater treatment process is escalating. How to dispose it properly is attracting much attention in society. Herein, solidifying residual sludge using magnesium oxychloride cement (MOC) is promising for converting it into building materials. Various factors of mass ratio (RW/S) of liquid to solid, molar ratio (Rn) of MgO to MgCl2 in MOC, mass ratio (Rm) of residual sludge to MOC, the mass concentration of Na2SiO3 (DNa2SiO3), and dosage of fly ash (DF) influenced the unconfined compression strength (RC) of the as–obtained MOC–solidified residual sludge, and it was characterized using SEM and XRD analysis. The results show that the value of RC for MOC–residual sludge solidified blocks increased initially and then decreased as Rn and Rm increased, respectively, for 60–day curing. At 10–day curing, equilibrium RC was reached at all RW/S values except 1.38, and at 60–day curing, RC decreased with RW/S increasing. The maximum RC of 60 days of 20.90 MPa was obtained at RW/S = 0.90, Rn = 5.0, and Rm = 1.00. Furthermore, adding Na2SiO3 or fly ash in the solidifying process could improve RC. The water resistance test showed that SM13 and NF5 samples exhibited good alkaline resistance after immersion for 7 and 14 days in an aqueous solution with pH = 7.0–11.0. The water resistance of MOC–residual sludge solidified blocks decreased with increase in immersion duration in aqueous solutions. The fly ash could also help improve water resistance of MOC–solidified residual sludge in neutral and basic aqueous solutions. This work provides an important theoretical basis and possibility for the efficient disposal and comprehensive utilization of residual sludge through solidification/stabilization technology using MOC from the perspective of mechanics and water resistance.

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Effects of Fly Ash and Hexadecyltrimethoxysilane on the Compressive Properties and Water Resistance of Magnesium Oxychloride Cement

Cited by 5 publications

References 26 publications

Magnesium Oxychloride Cement: Development, Opportunities and Challenges

Magnesium Oxychloride Cement: Development, Opportunities and Challenges

Mixture composition design of magnesium oxychloride cement-stabilized crushed stone materials applied as a pavement base

Mechanical Properties and Water Resistance of Magnesium Oxychloride Cement–Solidified Residual Sludge

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