Effect of sulfate on C-S-H at early age

The effect of increasing sulfate contents on the hydration of white cement was studied with a multi-technique approach. Quantitative X-Ray Diffraction (XRD) revealed that adding more gypsum in the cement resulted in more ettringite formation. Combining isothermal calorimetry, advanced in-situ 1H nuc...

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Bibliographic Details
Published in:Cement and concrete research 2020-12, Vol.138, p.106248, Article 106248
Main Authors: Bérodier, Elise M.J., Muller, Arnaud C.A., Scrivener, Karen L.
Format: Article
Language:English
Subjects:
C-S-H
Calcium silicate hydrate
Calorimetry
Cement
Cement paste
Depletion
Ettringite
Gel water
Gypsum
Hydration
Interlayers
Morphology
NMR
Nuclear magnetic resonance
Pores
Porosity
SEM
Sulfate
XRD
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Summary:The effect of increasing sulfate contents on the hydration of white cement was studied with a multi-technique approach. Quantitative X-Ray Diffraction (XRD) revealed that adding more gypsum in the cement resulted in more ettringite formation. Combining isothermal calorimetry, advanced in-situ 1H nuclear magnetic resonance (NMR) and early scanning electron microscopy (SEM) observations, it was possible to correlate the depletion of the gypsum with a change in C-S-H morphology, from needle-like to agglomerated C-S-H, together with a change in C-S-H gel pore content. Nevertheless, the content of C-S-H interlayer water remained similar and no change in C-S-H pore sizes were observed when increasing the sulfate content. The data allowed to calculate the volume composition of hydrated cement pastes at 3 days of hydration. The more gypsum was added to the cement, the lower was the bulk C-S-H volume due to lower gel pore content and the higher was the content of capillary porosity.
ISSN:0008-8846
1873-3948
DOI:10.1016/j.cemconres.2020.106248