scholarly journals Influence of Superhydrophobic Coating on the Water Resistance of Foundry Dust/Magnesium Oxychloride Cement Composite

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3431
Author(s):  
Fajun Wang ◽  
Xiantao Zhu ◽  
Huangjuan Liu ◽  
Sheng Lei ◽  
Daqi Huang
Keyword(s):  
Compressive Strength ◽  
Water Resistance ◽  
Cement Composite ◽  
Superhydrophobic Coating ◽  
X Ray Diffraction ◽  
Aqueous Emulsion ◽  
The Matrix ◽  
Magnesium Oxychloride ◽  
Magnesium Oxychloride Cement ◽  
Oxychloride Cement

In this work, magnesium oxychloride cement (MOC) was used to realize the resource use of foundry dust (FD). Portland cement (PC)-based superhydrophobic coating was prepared on the surface of FD/MOC composite to improve the water resistance of the composite. First, the FD/MOC composites with different contents of FD were prepared. The phase structure of the composite was analyzed using X-ray diffraction (XRD). The microstructure of the cross-section and surface of the composite was observed using field emission scanning electron microscope (FE-SEM). The mechanical properties of the FD/MOC composites with different FD contents at different ages were tested and analyzed. Secondly, the superhydrophobic coating was prepared on the surface of MOC composite using silane/siloxane aqueous emulsion as the hydrophobic modifier, PC as the matrix and water as the solvent. The microstructure and chemical composition of the PC-based superhydrophobic coating were tested and analyzed. The results show that FD can significantly improve the early strength of the FD/MOC composite. The 28-day compressive strength of the FD/MOC composite decreases with increasing FD content. When the FD content is 30%, the 28-day compressive strength of the FD/MOC composite is as high as 75.68 MPa. Superhydrophobic coating can effectively improve the water resistance of the FD/MOC composite. The softening coefficient of the FD/MOC composite without superhydrophobic coating is less than 0.26, while that of the composite modified by superhydrophobic coating is greater than 0.81.

Improved Magnesium Cement for Durable Hemp Composite Boards

2022 ◽  
Author(s):  
Jelizaveta Zorica ◽  
Maris Sinka ◽  
Genadijs Sahmenko ◽  
Diana Bajare
Keyword(s):  
Compressive Strength ◽  
Water Resistance ◽  
Chemical Reactivity ◽  
Ease Of Use ◽  
Lower Amount ◽  
Insulation Material ◽  
Magnesium Oxychloride ◽  
Magnesium Oxychloride Cement ◽  
Cement Board ◽  
Oxychloride Cement

Hemp concrete is a well-known bio-based building material, but due to its relatively low compressive strength is mainly used as an insulation material with a load-bearing wooden frame. There are possibilities to expand hemp concrete application in construction by substituting traditional lime with magnesium cement. Magnesium oxychloride cement is a material already known for some time and nowadays used in building board production. Strength, lightweight, ease of use are advantages that highlight relatively new magnesium oxychloride type boards compared to traditional sheeting materials such as plywood, gypsum plasterboard and fibre-cement board. Therefore, similar parameters are thought to be reached by producing magnesium oxychloride hemp board. In this work, magnesium cement water resistance was studied and possibilities to improve it was examined by adding fly ash and nanosilica. Among the nanomaterials used in building materials, nanosilica has gained significant interest by performing a beneficial effect in improving the mechanical properties of concretes. In addition, due to its ultrafine size and high chemical reactivity, the performance of nanosilica is much better with a lower amount of admixture required. Results show that applied nanosilica slightly reduced the compressive strength of magnesium cement in a dry state, but at the same time significantly increased its water resistance. Hemp magnesium oxychloride cement board prototype samples were produced and demonstrate promising results for further manufacturing of hemp composite boards.

scholarly journals Effect of Calcination Temperature on Mechanical Properties of Magnesium Oxychloride Cement

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 607
Author(s):  
Chenggong Chang ◽  
Lingyun An ◽  
Rui Lin ◽  
Jing Wen ◽  
Jinmei Dong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Calcination Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Magnesium Oxychloride ◽  
Magnesium Oxychloride Cement ◽  
Scanning Electron ◽  
Oxychloride Cement

In order to make full use of magnesium chloride resources, the development and utilisation of magnesium oxychloride cement have become an ecological and economic goal. Thus far, however, investigations into the effects on these cements of high temperatures are lacking. Herein, magnesium oxychloride cement was calcinated at various temperatures and the effects of calcination temperature on microstructure, phase composition, flexural strength, and compressive strength were studied by scanning electron microscopy, X-ray diffraction, and compression testing. The mechanical properties varied strongly with calcination temperature. Before calcination, magnesium oxychloride cement has a needle-like micromorphology and includes Mg(OH)2 gel and a trace amount of gel water as well as 5 Mg(OH)2·MgCl2·8H2O, which together provide its mechanical properties (flexural strength, 18.4 MPa; compressive strength, and 113.3 MPa). After calcination at 100 °C, the gel water is volatilised and the flexural strength is decreased by 57.07% but there is no significant change in the compressive strength. Calcination at 400 °C results in the magnesium oxychloride cement becoming fibrous and mainly consisting of Mg(OH)2 gel, which helps to maintain its high compressive strength (65.7 MPa). When the calcination temperature is 450 °C, the microstructure becomes powdery, the cement is mainly composed of MgO, and the flexural and compressive strengths are completely lost.

scholarly journals Study on Preparation and Properties of Intrinsic Super-Hydrophobic Foamed Magnesium Oxychloride Cement Material

2020 ◽  
Vol 10 (22) ◽  
pp. 8134
Author(s):  
Jiaxin Huang ◽  
Shaojin Ge ◽  
Hongning Wang ◽  
Ruoyu Chen
Keyword(s):  
Compressive Strength ◽  
Absorption Rate ◽  
Water Resistance ◽  
Moisture Absorption ◽  
Engineering Application ◽  
Chemical Corrosion ◽  
Cement Material ◽  
Magnesium Oxychloride ◽  
Magnesium Oxychloride Cement ◽  
Oxychloride Cement

As we all know, magnesium oxychloride foamed cement material has poor water resistance, leading to a decline in application value. In our research, tetraethylorthosilicate (TEOS) and triethoxy-1H, 1H, 2H, 2H-tridecylfluoro-n-octylsilane (FAS) were pre-cohydrolyzed to prepare the overall super hydrophobic magnesium oxychloride cement (MOC) foamed material, and its structure and performances were systematically studied. The results show that adding organosilane can make it have overall hydrophobicity under the premise of maintaining the compressive strength. Mechanical abrading and chemical corrosion tests show its good engineering durability. The maximum moisture absorption rate dropped by 16.2%, and the quality can be restored to 98.1% of the original quality after dehumidification. All these properties show that the hydrophobic foamed magnesium oxychloride cement has potential engineering application value.

Effect of hydroxyacetic acid on the water resistance of magnesium oxychloride cement

2020 ◽  
Vol 246 ◽  
pp. 118428 ◽  
Author(s):  
Xueru Luo ◽  
Wenqiang Fan ◽  
Chunqing Li ◽  
Yong Wang ◽  
Hongjian Yang ◽  
...  
Keyword(s):  
Water Resistance ◽  
Magnesium Oxychloride ◽  
Magnesium Oxychloride Cement ◽  
Hydroxyacetic Acid ◽  
Oxychloride Cement
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