M. Mägi

A high resolution 29Si NMR study of the hydration of tricalciumsilicate

Abstract A new method for the determination of the structure of silicate anions, formed during hydration of tricalciumsilicate Ca3SiO5 (C3S), is presented. High resolution solid state 29Si NMR spectra of C3S and its hydration products, formed during selected reaction times from 6 hours to 130 days, provide the kinetics of formation of the end groups and of the middle groups in silicate chains.

Solid-state high-resolution 29Si NMR spectroscopy of synthetic 14 Å, 11 Å and 9 Å tobermorites

Abstract A new method for the investigation of the structure of silicates - solid-state high-resolution 29 Si NMR spectroscopy - was used for the investigation of 14 A, 11 A and 9 A tobermorites prepared under different conditions. It is possible to determine selectively the individual SiO 4 structural units in tobermorites (end groups, chain middle groups, branching sites, etc.) and to draw conclusions about the type and structure of the silicate anions in the lattice. Synthetic 14 A tobermorite consists predominantly of single chains, the 11 A and 9 A tobermorites contain, depending on the method of preparation, double chains and/or single chains.

High-resolution solid-state 29Si NMR of polymorphs of Ca2SiO4

High-resolution solid-state 29Si NMR spectra of four (γ, β, αL1 and α) polymorphs of Ca2SiO4 have been measured. The isotropic silicon 29Si chemical shifts lie between −73.5 and −70.1 ppm, and increasing coordination number of calcium leads to low-field 29Si shifts. The 29Si shifts in combination with the linewidth information allow to identify the C2S phases by 29Si NMR.

Solid-state high-resolution 29Si mas MAR of silicates with sixfold coordinated silicon

Abstract A correlation between isotropic 29chemical shifts and mean Si-O bond length is presented for ten silicates containing sixfold coordinated silicon. The 29Si chemical shift data afford a measure of the cationic, neutral or anionic character of the octahedral silicon.

Ba7[Si7O21].~10BaCl2 - a compound with a new type of cyclic silicate anions

Etude de la constitution des anions silicate par la methode molybdique, par chromatographie sur papier, par spectre RMN de 29 Si, par la methode de la substitution de cations par le radical trimethylsilyl suivie de la caracterisation des produits de la reaction par chromatographie en phase vapeur et spectrometrie de masse. Mise en evidence danions cycloheptasilicates [Si 7 O 21 ] 14−