Synthesis and structural characterisation of new ettringite and thaumasite type phases: Ca6[Ga(OH)6·12H2O]2(SO4)3·2H2O and Ca6[M(OH)6·12H2O]2(SO4)2(CO3)2, M = Mn, Sn

Norman, Rachel L.; Dann, Sandra E.; Hogg, Simon C.; Kirk, Caroline A.

doi:10.1016/j.solidstatesciences.2013.08.006

Cited by 21 publications

(10 citation statements)

References 24 publications

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“…Unfortunately, to date, we have not fully understood the electronic structures of the thaumasite. Experimentally, thaumasite is found to feature an extremely similar crystal structure and morphology with ettringite, but the differences in their physical information have not been provided yet. This impedes our understanding of the failure mechanisms of the 2 types sulfate attacks.…”

Section: Introductionmentioning

confidence: 99%

Understanding the atomic and electronic origin of mechanical property in thaumasite and ettringite mineral crystals

San

Tao

et al. 2018

J Am Ceram Soc

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Ettringite and thaumasite are 2 of the relevant secondary products in portland cement minerals. They are rare crystals with high water content. Two density functional theory based ab initio packages VASP and the OLCAO were used for exploring the geometry structure, electronic, and mechanical properties of ettringite and thaumasite. The calculations focus on the comparison of their structures and properties to gain insights that can reveal the minute difference in properties due to differences in their structure, composition and water content. Detailed analysis of interatomic bonding shows the similarities and subtle difference between them even though thaumasite has the Si tetrahedron as the backbone unit in contrast to ettringite with Al‐columns and no Si atoms. Moreover, thaumasite has strong C–O bonds that are absent in ettringite, and ettringite has far more water molecules with a substantial contribution from the hydrogen bonding. It is shown that the role played by relatively strong S–O bonds in both crystals has a large impact on the hydration in these crystals. On the basis of calculated total bond order density, it is concluded that thaumasite is slightly more cohesive than ettringite consistent with the calculated mechanical properties. The detailed comparative results for these 2 important minerals we obtained in this paper, many of them for the first time, will pave the way to understanding the structure and electronic structure origin of other more complex cement crystals.

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Section: Introductionmentioning

confidence: 99%

Understanding the atomic and electronic origin of mechanical property in thaumasite and ettringite mineral crystals

San

Tao

et al. 2018

J Am Ceram Soc

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“…This indicated that both AFt and AFm stabilized Mn into the crystal structure and formed (Mn, Al, Fe)‐AFt as the TEM results (Figure 10) showed. Mn was mainly located at the octahedral site occupied by Al ions in AFt 42,66 . The low Fe concentration in solution was attributed to the formation of the amorphous FeOOH phase 12 and a solid solution between Al‐ettringite and Fe‐ettringite with a miscibility gap in the range of 0.3 < Al/(Al + Fe) < 0.6 26 .…”

Section: Resultsmentioning

confidence: 99%

“…Mn was mainly located at the octahedral site occupied by Al ions in AFt. 42,66 The low Fe concentration in solution was attributed to the formation of the amorphous FeOOH phase 12 and a solid solution between Al-ettringite and Fe-ettringite with a miscibility gap in the range of 0.3 < Al/(Al + Fe) < 0.6. 26 The formed (Al, Fe)-AFt solid solution caused the peak shift in XRD results (Figure 9A, the enlarged figure).…”

Section: Hydration Processmentioning

confidence: 99%

In‐depth understanding the hydration process of Mn‐containing ferrite: A comparison with ferrite

et al. 2022

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Manganese (Mn) is inevitably incorporated into cement from raw materials, and is mainly incorporated into the ferrite phase of cement. In this paper, the hydration kinetic was investigated for Mn‐containing ferrite and unmodified ferrite. The evolution of the solid phases, aqueous species, and both conductivity and pH were investigated for unmodified ferrite and Mn‐containing ferrite by a diluted suspension experiment. Isothermal calorimetry, transmission electron microscopy, and mechanical property measurements were conducted to explore the influence of Mn on the hydraulic activity of ferrite. The results showed that the incorporation of Mn enhances the hydraulic activity, alleviates the influence of gypsum on the retardation of ferrite, and improves the early strength in the presence of gypsum. Mn‐containing ferrite also accelerates dissolution, influencing the initial sulfate adsorption. Mn ions eventually incorporate into (Al, Fe)‐AFt and (Al, Fe)‐AFm. During the first several hours of hydration of ferrite, there is no sulfate consumption after the initial adsorption, accompanied by a decrease of Ca2+ and Al3+ concentration. And an “adsorption‐barrier” hypothesis is proposed to explain the dormant period of sulfate consumption.

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“…8 In addition, this compound also forms via the hydration of calcium aluminates in the presence of sulfate during the early hydration process of Portland cement. 9 Particularly, ettringite is well-known as an anion-exchanger, and the generic formula for ettringite could be expressed as [M x 2+ (M 3+ ) x/3 (OH) 12 ][A nÀ ] x/n $ 26H 2 O, where M 2+ is a divalent cation, including Ca 2+ , Sr 2+ , Pb 2+ , Co 2+ , Zn 2+ , etc., [10][11][12] M 3+ is a trivalent cation, including Al 3+ , Ga 3+ , Fe 3+ , Mn 3+ , Cr 3+ , etc., 13,14 and A nÀ is an n-valent anion, including Cl À , SO 4 2À , SeO 4 2À , AsO 4 3À , etc. 10,[15][16][17] Based on the previously reported structure model of ettringite, 18 the unit cell mainly consists of column parts {Ca 6 [Al(OH) 6 S1 in the ESI †).…”

Section: Introductionmentioning

confidence: 99%

Structural transformation of selenate ettringite: a hint for exfoliation chemistry

2017

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Synthesis and structural characterisation of new ettringite and thaumasite type phases: Ca6[Ga(OH)6·12H2O]2(SO4)3·2H2O and Ca6[M(OH)6·12H2O]2(SO4)2(CO3)2, M = Mn, Sn

Cited by 21 publications

References 24 publications

Understanding the atomic and electronic origin of mechanical property in thaumasite and ettringite mineral crystals

Understanding the atomic and electronic origin of mechanical property in thaumasite and ettringite mineral crystals

In‐depth understanding the hydration process of Mn‐containing ferrite: A comparison with ferrite

Structural transformation of selenate ettringite: a hint for exfoliation chemistry

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