Magnesium and calcium silicate hydrates, Part I: Investigation of the possible magnesium incorporation in calcium silicate hydrate (C-S-H) and of the calcium in magnesium silicate hydrate (M-S-H) - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Applied Geochemistry Année : 2018

Magnesium and calcium silicate hydrates, Part I: Investigation of the possible magnesium incorporation in calcium silicate hydrate (C-S-H) and of the calcium in magnesium silicate hydrate (M-S-H)

Résumé

Calcium silicate hydrate (C-S-H) and magnesium silicate hydrate (M-S-H) have been described as two separatephases. This work investigates their stability domains and the possible uptake of small amounts of magnesium byC-S-H or, reversely, the uptake of small amounts of calcium by M-S-H. The phases, synthesized by co-precipitation,are characterized using a large panel of techniques (thermogravimetry analysis, X-ray diffraction, Xraypair distribution function analysis, 29Si MAS-NMR spectroscopy, measurement of zeta potential and cationexchange capacity) while the compositions of the solutions at equilibrium are determined by ion chromatographyand pH measurements. Syntheses of C-S-H samples in the presence of magnesium ((Ca + Mg)/Si = 0.80and Mg/Si = 0.05 or 0.10) yield two separate phases: C-S-H and M-S-H. There is no experimental evidence ofany uptake of magnesium by C-S-H. On the contrary, when M-S-H samples are synthesized in the presence ofcalcium ((Ca + Mg)/Si = 0.80 and Ca/Si = 0.05 or 0.10), the low pH of the suspension (9–10) prevents theformation of C-S-H but favors the precipitation of M-S-H with small amounts of calcium. This latter may besorbed onto the surface of M-S-H to outbalance its negative charges and/or incorporated into the interlayer, assuggested by small structural changes.

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hal-02021043 , version 1 (19-03-2024)

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Ellina Bernard, Barbara Lothenbach, Céline Cau-Dit-Coumes, Christophe Chlique, Alexandre Dauzeres, et al.. Magnesium and calcium silicate hydrates, Part I: Investigation of the possible magnesium incorporation in calcium silicate hydrate (C-S-H) and of the calcium in magnesium silicate hydrate (M-S-H). Applied Geochemistry, 2018, 89, pp.229-242. ⟨10.1016/j.apgeochem.2017.12.005⟩. ⟨hal-02021043⟩
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