{"title":"Further study of the erosion mechanism of calcium salt on 517 phase","authors":"Yan Guan, Xiao Han, Zhiqi Hu","doi":"10.1680/jadcr.23.00078","DOIUrl":null,"url":null,"abstract":"As the main hydration product of magnesium oxysulfate (MOS) cement, 517 phase (5Mg(OH)<sub>2</sub>·MgSO<sub>4</sub>·7H<sub>2</sub>O) is one of the main sources of MOS cement strength. At present, the experimental results show that calcium ions have a great influence on the stability of 517 phase, so this paper mainly explores the erosion process and mechanism of calcium ions on 517 phase. The 517 phase with 94.56 % purity was synthesized in this paper, and the erosion effect of different calcium salts on 517 phase was also characterized, where thermogravimetric-differential scanning calorimetry (TG-DSC), scanning electron microscope (SEM), transmission electron microscope (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD) were used to analyze the performance changes of 517 phase under different calcium salt erosion. The results show that in the solution, Ca<sup>2+</sup> combined with SO<sub>4</sub><sup>2+</sup> in 517 phase, resulting in an increase in the spacing between the MgO<sub>6</sub> octahedron layers in 517 phase thus destroying the structure of 517 phase. Moreover, when ions diffused, MgO<sub>6</sub> octahedron and Cl<sup>2+</sup> recombined into 518 phase (5Mg(OH)<sub>2</sub>·MgCl<sub>2</sub>·8H<sub>2</sub>O). In addition, insoluble weddellite was also found to erode 517 phase to a certain extent, while the 517 phase blended with gypsum was stable. The simulation results of molecular dynamics also showed that Ca<sup>2+</sup> had better adsorption ability for SO<sub>4</sub><sup>2+</sup> and Cl<sup>2+</sup> than Mg<sup>2+</sup>. When it was in contact with 517 phase, Ca<sup>2+</sup> was absorbed near SO<sub>4</sub><sup>2+</sup> and Cl<sup>2+</sup> was brought into the system.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":"261 1","pages":""},"PeriodicalIF":1.4000,"publicationDate":"2023-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Advances in Cement Research","FirstCategoryId":"5","ListUrlMain":"https://doi.org/10.1680/jadcr.23.00078","RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CONSTRUCTION & BUILDING TECHNOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
As the main hydration product of magnesium oxysulfate (MOS) cement, 517 phase (5Mg(OH)2·MgSO4·7H2O) is one of the main sources of MOS cement strength. At present, the experimental results show that calcium ions have a great influence on the stability of 517 phase, so this paper mainly explores the erosion process and mechanism of calcium ions on 517 phase. The 517 phase with 94.56 % purity was synthesized in this paper, and the erosion effect of different calcium salts on 517 phase was also characterized, where thermogravimetric-differential scanning calorimetry (TG-DSC), scanning electron microscope (SEM), transmission electron microscope (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD) were used to analyze the performance changes of 517 phase under different calcium salt erosion. The results show that in the solution, Ca2+ combined with SO42+ in 517 phase, resulting in an increase in the spacing between the MgO6 octahedron layers in 517 phase thus destroying the structure of 517 phase. Moreover, when ions diffused, MgO6 octahedron and Cl2+ recombined into 518 phase (5Mg(OH)2·MgCl2·8H2O). In addition, insoluble weddellite was also found to erode 517 phase to a certain extent, while the 517 phase blended with gypsum was stable. The simulation results of molecular dynamics also showed that Ca2+ had better adsorption ability for SO42+ and Cl2+ than Mg2+. When it was in contact with 517 phase, Ca2+ was absorbed near SO42+ and Cl2+ was brought into the system.
期刊介绍:
Advances in Cement Research highlights the scientific ideas and innovations within the cutting-edge cement manufacture industry. It is a global journal with a scope encompassing cement manufacture and materials, properties and durability of cementitious materials and systems, hydration, interaction of cement with other materials, analysis and testing, special cements and applications.