Silicon Substitution for Aluminum in Calcium Silicate Hydrates

Abstract

27 Al MAS and multiquantum (MQ) MASNMR (magicangle spinning nuclear magnetic resonance) spectroscopy were used to study the substitution of silicon by aluminum in calcium silicate hydrates (C-S-H), which are the main component of hydrated portland cement. Synthetic C-S-H samples were prepared, and their chemical stability was studied. Two-dimensional 3Q-MASNMR spectra revealed the chemical shift and quadrupolar parameters (␦ iso , Q ) that labeled aluminum sites in the C-S-H. Tetrahedral aluminum was observed in the bridging and nonbridging sites of the silicate chains.

Solid state NMR investigations on the role of organic admixtures on the hydration of cement pastes

“…In accordance with the literature on cement hydration kinetics [1][2][3][4][5][6][7][8][9] and in combination with previous studies of synthetic calcium aluminate clinker minerals [19,20] correlation between the 27 Al NMR signals and defined crystal structures within the inorganic phase is given. Because of the inherent broad lines of the 27 Al quadrupole moment, resulting in an additional spectral broadening, one-dimensional NMR methods are predominant in the literature [15,[19][20][21][22][23]25]. 29 Si NMR of hardened cement pastes and quartz samples is limited by the long relaxation times (T 1 > 20 s) of the silicon atoms within the quartz and the hardened cement, requiring long measuring times.…”

“…Several contributions to the hydration and hardening of cement pastes as determined by using 27 Al and 29 Si NMR methods are available in the literature [19][20][21][22][25][26][27][28]. Here, we extend these to organically modified systems to monitor the influence of the organic components on the cement paste at the molecular level.…”

“…Within this study solid state NMR [14][15][16][17] is applied for the analysis of the individual components, the fresh and the hardened cement pastes [18][19][20][21][22][23][24]. Several contributions to the hydration and hardening of cement pastes as determined by using 27 Al and 29 Si NMR methods are available in the literature [19][20][21][22][25][26][27][28].…”

The Relationship Between 27Al Quadrupolar Parameters and AlF63– Octahedron Connectivity in Crystalline and Glassy Fluoroaluminates

“…This hinders the precise determination of the quadrupolar parameters, especially when several crystallographically independent Al sites are present in the compound. However, the development of techniques such as SAtellite TRAnsition Spectroscopy (SATRAS), [1,2] and Multiple Quantum Magic Angle Spinning (MQ-MAS), [3] which are able to average first-and second-order broadenings, have allowed high-resolution 27 Al NMR spectra to be recorded from which the quadrupolar parameters in crystalline compounds, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and their distributions in disordered phases, [16,[21][22][23][24][25][26][27][28][29][30] can be accurately determined.…”

Compatibility Investigations on Polymer‐Fiber‐Reinforced Cements Modified with Polymer Latexes

“…[20] Solid-state NMR spectroscopy [21][22][23][24] was applied to monitor the bulk composition of both the hardened cement and the polymer fibers, and its changes during the hydration process, while scanning electron microscopy [25,26] enabled the visualization of the fiber surfaces, and the particle shapes of the hydrated cement phases and the latex. Several contributions to the hydration and hardening of cement pastes, as determined from 1 H, 27 Al and 29 Si NMR spectroscopy [23,24,[27][28][29][30][31][32][33] and scanning electron microscopy, and of polymer-fiber-modified cements [7][8][9] are available in the literature, and are extended to a microscopic level. In particular the 27 Al NMR signals can be correlated to defined crystal structures within the inorganic phase.…”