Nuclear Magnetic Resonance Spectroscopy of Cement-Based Materials 1998
DOI: 10.1007/978-3-642-80432-8_10
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29Si MAS NMR Spectroscopy of Poorly-Crystalline Calcium Silicate Hydrates (C-S-H)

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Cited by 15 publications
(65 citation statements)
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“…At high Ca/Si ratios, the Q b 2 peak is not clearly resolved, reflecting that the silicate chains become shorter and that the C-S-H is mainly composed of silicate dimers. Again, this is in accord with earlier 29 Si MAS NMR [23][24][25][26][27][28][29][30] and Raman spectroscopic [31] studies of synthesized C-S-H samples and it reflects that the high-Ca/Si ratio C-S-H samples (Ca/Si~1.5) have a defect tobermorite-like structure, with silicon absent from almost all bridging tetrahedral sites, rather than a jennite-like structure [21], which ideally contains Q 2 sites only (infinite silicate chains). The 29 Si MAS NMR spectra in Fig.…”
Section: Nmr Measurementssupporting
confidence: 92%
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“…At high Ca/Si ratios, the Q b 2 peak is not clearly resolved, reflecting that the silicate chains become shorter and that the C-S-H is mainly composed of silicate dimers. Again, this is in accord with earlier 29 Si MAS NMR [23][24][25][26][27][28][29][30] and Raman spectroscopic [31] studies of synthesized C-S-H samples and it reflects that the high-Ca/Si ratio C-S-H samples (Ca/Si~1.5) have a defect tobermorite-like structure, with silicon absent from almost all bridging tetrahedral sites, rather than a jennite-like structure [21], which ideally contains Q 2 sites only (infinite silicate chains). The 29 Si MAS NMR spectra in Fig.…”
Section: Nmr Measurementssupporting
confidence: 92%
“…Jennite (Ca 9 Si 6 O 18 (OH) 6 ·8H 2 O [21]) exhibits Ca/Si = 1.5 and Ca/Si = 1.75 corresponds to the ratio typically found in mature Portland cement pastes [22]. For the low-Ca/Si ratio samples, three distinct peaks are resolved, corresponding to end groups and dimers (Q 1 , −79.1 ppm), the bridging sites (Q b 2 , −83.2 ppm) and paired sites (Q p 2 , −84.9 ppm) of the silicate chains, in agreement with earlier 29 Si MAS NMR studies of synthesized C-S-H phases [23][24][25][26][27][28][29][30]. Moreover, the observation of these resonances agrees with the basic dreierketten silicate-chain structure of 14-Å tobermorite [19], although infinite chains in the ideal structures are not observed for the synthesized samples.…”
Section: Nmr Measurementssupporting
confidence: 82%
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“…This shoulder has been observed by a number of investigators [3,4,19,31,[64][65][66][67], but its assignment is still uncertain. It is generally assumed that the shoulder is produced by a subset of the Q 2 Si, and it is likely to represent at least some of those present as bridging tetrahedra [4,67]. The current results are consistent with (but not proof of) this last hypothesis, as the shoulder becomes increasingly prominent as the Ca/Si ratio decreases.…”
Section: Ca Concentration Versus Ca/si Of the Solidmentioning
confidence: 87%