Si NMR Study of the Hydration of Ca3SiO5 and ß‐Ca2SiO4 in the Presence of Silica Fume

Abstract

29 Si magic-angle spinning nuclear magnetic resonance (MASNMR) was used to study the room-temperature hydration of C 3 S, ␤-C 2 S, and reactive ␤-C 2 S mixed with different amounts of silica fume (SF) that had been hydrated up to nine months and longer. The overall CaO:SiO 2 molar ratios of the mixes were 0.12, 0.20, 0.35, 0.50, and 0.80. NMR spectroscopy was used to quantify the remaining starting materials and the resulting hydration products of different species. A broad peak assigned to Q 3 , appearing in both the fourier transform (FT) and the cross-polarization (CP) modes, increased in intensity with increased SF content and with age. This Q 3 species was attributed to two sources: (1) the surface hydroxylation of SF and (2) the cross-linking of dreierketten (chains of silicate tetrahedra arranged in a repeating three-unit conformation) in the calcium silicate hydrate (C-S-H) structure. A Q 4 species also appeared in the CP spectra of samples with large SF additions after extended hydration and was attributed to cross-polarization by adjacent hydroxylated Q 3 species at the surface of amorphous SiO 2 . †

Degree of reaction and phase content of silica-based one-part geopolymers investigated using chemical and NMR spectroscopic methods

“…These changes are most likely related to the alteration of the silica surface during dissolution. This interpretation is in line with previous studies [31,32] in which it was observed that dissolution of microsilica in alkaline (Ca-dominated) media led to the formation of Q 3 species. These were assigned fully [31] or in large part [32] to the silica; in the latter study, it was shown by 1 H- 29 Si CP MAS NMR that these species can be assigned to a hydrated layer on the surface of the microsilica.…”

“…This interpretation is in line with previous studies [31,32] in which it was observed that dissolution of microsilica in alkaline (Ca-dominated) media led to the formation of Q 3 species. These were assigned fully [31] or in large part [32] to the silica; in the latter study, it was shown by 1 H- 29 Si CP MAS NMR that these species can be assigned to a hydrated layer on the surface of the microsilica. Another study [33] found that formation of a significant amount of Q 3 species took place also during dissolution of microsilica in 1 M NaOH solution, but no unequivocal assignment was given.…”

Estudio por difracción de rayos X de la hidratación de mezclas de CaAl₂O₄ - Humo de silice

“…These results have been confirmed by Thermogravimetry, Differential Thermal Analysis and Scanning Electric Microscopy. The hydration mechanism proposed confirms previous data of Nuclear Magnetic Resonance of Solids (RMN) of 29 Si of the authors of this paper. …”

“…The evolution of the hydrated phases, formed in the first instants of the reaction, has been studied by laboratory X ray diffraction with a time resolution of 36 min. 29 Si of the authors of this paper.…”

“…Los resultados obtenidos por Análisis Térmico Diferencial (ATD) y Termogravimétrico (TG) y Microscopia Electrónica de Barrido de Emisión de Campo (MEB) han confirmado los resultados obtenidos por difracción de rayos X. El mecanismo de hidratación propuesto esta igualmente apoyado en datos de resonancia magnética nuclear de 29 Si obtenidos por los presentes autores (17,18). …”