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New insights on thaumasite precipitation based on thermodynamic modeling and 3-year exposure of cement pastes to Na₂SO₄ and MgSO₄ solutions
File(s)
Author(s)
Miyamoto, Shintaro
Kawabata, Yuichiro
Yoshida, Natsuki
Yio, Marcus HN
Saito, Tsuyoshi
Type
Journal Article
Abstract
Cement pastes were exposed to 0.10 mol/L Na2SO4 and MgSO4 solutions at 20 °C for over three years to investigate the precipitation mechanism of thaumasite and the associated phase evolution. Powder X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy show that samples exposed to MgSO4 have lower contents of portlandite, calcite, and C-S-H, compared to those exposed to Na2SO4. In addition, samples exposed to MgSO4 contained significant amounts of thaumasite and brucite. Ettringite content is comparable in both conditions, but thaumasite is not detectable in samples exposed to Na2SO4. This difference can be attributed to the higher degree of supersaturation of thaumasite in samples exposed to MgSO4 compared to Na2SO4. Thermodynamic modelling was carried out to validate this hypothesis and the predicted phase assemblages show good consistency with experiments. By introducing a critical supersaturation into the thermodynamic phase equilibrium calculations, the model successfully reproduced the selective precipitation of thaumasite in samples exposed to MgSO4.
Date Issued
2025-10-01
Date Acceptance
2025-06-10
Citation
Cement and Concrete Composites, 2025, 163
URI
URL
DOI
ISSN
0958-9465
Publisher
Elsevier
Journal / Book Title
Cement and Concrete Composites
Volume
163
Copyright Statement
© 2025 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Subjects
BEHAVIOR
CONCRETE
Construction & Building Technology
Critical supersaturation
CRYSTAL-STRUCTURE
DURABILITY
GYPSUM
MAGNESIUM-SULFATE ATTACK
Materials Science
Materials Science, Composites
MECHANISM
MgSO4
MORTARS
Science & Technology
SODIUM
SOUTHERN CALIFORNIA
Sulfate attack
Technology
Thaumasite formation
Thermodynamic phase equilibrium
Publication Status
Published
Article Number
106190
Date Publish Online
2025-06-11