29Si MAS NMR study of the structure of calcium silicate hydrate

doi:10.1016/S1065-7355(96)90046-2

Advanced Cement Based Materials

Volume 3, Issues 3–4, April–May 1996, Pages 144-156

https://doi.org/10.1016/S1065-7355(96)90046-2 Get rights and content

Abstract

This paper presents the results of a comprehensive investigation of single-phase calcium silicate hydrate (CSH) with known compositions using the combined capabilities of ²⁹Si magic angle spinning (MAS) NMR, powder X-ray diffraction (XRD), and chemical analysis of the solution and solid. CSH gels with C/S ratios ranging from 0.4 to 1.85 have been synthesized by hydration of highly reactive β-C₂S and aqueous reaction of fumed silica with CaO and separately with highly reactive β-C₂S. The main findings include the following. (1) CSH shows continuity and diversity in both composition and structure and forms a continuous structural series. (2) Phase-pure CSH has C/S ratios between 0.6–1.54. (3) SiOH and CaOH bonds both occur in CSH, with the abundance of the former decreasing and that of the latter increasing with increasing C/S ratio. Model calculation indicates that there are between 0.13–0.43 SiOH bonds per tetrahedron and the CaOH/Ca ratio varies between nearly 0 and 0.64. An ideal formula for CSH with a C/S ratio of 1.5 is: Ca_4.5[Si₃O₈(OH)](OH)₄ · nH₂O. A defect-tobermorite structural model is proposed for CSH in which individual layers have the basic structure of 1.4-nm tobermorite but contain a significant concentration of defects and are more disordered. Stacking disorder between adjacent layer and disorder within individual layers may both contribute to the local and long-range disorder and thus to the diversity of CSH.

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29Si MAS NMR study of the structure of calcium silicate hydrate

Abstract

Cem. Concr. Res.

Cem. Concr. Res.

Cem. Concr. Res.

Cem. Concr. Res.

Cem. Concr. Res.

Cem. Conc. Res.

J. Euro. Ceram. Soc.

Cem. Concr. Res.

Cem. Concr. Res.

Cem. Concr. Res.

Adv. Cem. Based Mater.

J. Chem. Soc.

Adv. Chem. Ser.

Nature

J. Am. Ceram. Soc.

Concrete

Cement Chemistry

J. Am. Chem. Soc.

J. Chem. Soc.

J. Am. Ceram. Soc.

J. Am. Ceram. Soc.

J. Am. Ceram. Soc.

Adv. Cem. Res.

J. Am. Ceram. Soc.

J. Am. Ceram. Soc.

²⁹Si MAS NMR study of the structure of calcium silicate hydrate