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

Saro San, Neng Li, Yong Tao, Wenqin Zhang, Wai Yim Ching

Research output: Journal article publicationJournal articleAcademic researchpeer-review

16 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)5177-5187
Number of pages11
JournalJournal of the American Ceramic Society
Volume101
Issue number11
DOIs
Publication statusPublished - Nov 2018
Externally publishedYes

Keywords

  • ab initio calculation
  • atomic and electronic structures
  • ettringite
  • mechanical properties
  • thaumasite

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

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