4.7 Article

The physiochemical alterations of calcium silicate hydrate (C-S-H) under magnesium attack

期刊

CEMENT AND CONCRETE RESEARCH
卷 160, 期 -, 页码 -

出版社

PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.cemconres.2022.106901

关键词

Calciumsilicatehydrate(C-S-H); Magnesiumchloride; Magnesiumsulfate; Magnesiumsilicatehydrate(M-S-H); Durability

资金

  1. National Natural Science Foundation of China [51890904, 52122802, 52078126, 51825203]
  2. Science and Technology Innovation 2025 Major Project of Ningbo [2020Z040, CP15]
  3. Scientific Research Foundation of Graduate School of Southeast University [YBPY2144]
  4. National Natural Science Foundation of China [51890904, 52122802, 52078126, 51825203]
  5. Science and Technology Innovation 2025 Major Project of Ningbo [2020Z040]
  6. Innovandi-The Global Cement and Concrete Research Nextwork [CP15]
  7. Scientific Research Foundation of Graduate School of Southeast University [YBPY2144]
  8. Singapore MOE Tier1 [51890904]
  9. [WBS R-302- 000-242-133]

向作者/读者索取更多资源

This study comprehensively analyzes the effects of magnesium on the physiochemical properties of C-S-H. The stability of C-S-H is impaired under magnesium attack, leading to the precipitation of M-S-H and brucite on its surface. The dominance of M-S-H phase increases with higher magnesium concentrations. The Ca/Si and Mg/Si ratios of hydrates increase with the Ca/Si ratio of starting C-S-H samples. A small amount of magnesium may enter the C-S-H structure after exposure to magnesium solution, presenting a different binding energy compared to pure M-S-H. Anion types have a limited influence on the deterioration of C-S-H, except when sulfate ions are present and gypsum is observed.
The interaction of magnesium and calcium silicate hydrate (C-S-H) is of importance in the realm of cement chemistry given the need for sustainable binders and durability concerns. In this paper, comprehensive analyses were conducted to reveal the effects of magnesium on the physiochemical properties of C-S-H. Three factors including anion types, concentrations of magnesium solution as well as the Ca/Si ratio of the starting C-S-H samples were considered. It is demonstrated that the stability of C-S-H is impaired under magnesium attack. Magnesium silicate hydrate (M-S-H) and/or brucite are prone to precipitate on the surface of C-S-H samples after being attacked by 0.05 mol/L magnesium, which accounts for the high amount of magnesium measured by EDS. In contrast, at a magnesium concentration of 0.5 mol/L, M-S-H with a trace amount of calcium becomes the dominating phase. The Ca/Si and Mg/Si ratios of hydrates show an increase with the Ca/Si ratio of starting C-S-H samples. The XPS results indicate that a small amount of magnesium may enter into the C-S-H structure after exposure to 0.05 mol/L magnesium solution, presenting a different Mg 1s binding energy compared with pure M-S-H. Anion types do not exhibit a pronounced influence on the deterioration of C-S-H, except gypsum is observed in the hydrates when sulfate ions are present.

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