Table 2. Relative abundance of the different 29Si sites retrieved from analysis of 29Si MAS NMR data, mean Si chain length, and maximum Ca/Si ratio that could be reached if the charge resulting from all vacant Si tetrahedra was compensated for by interlayer Ca (Ca/Si max).
n.d. stands for ‘not detected’.
| Relative abundance of the different 29Si sites (%) | |||||
|---|---|---|---|---|---|
| Sample | Q 1 | Q 2 | Q 3 | Mean chain length (number of Si tetrahedra) | Ca/Si max† |
| CSH 0.6–323 K | 4.2 ± 1.5 | 55.6 ± 3.0 | 40.2 ± 1.5 | 48 | 1.02 |
| CSH 0.6–443 K | 4.0 ± 1.8 | 53.6 ± 3.6 | 42.4 ± 1.8 | 50 | 1.02 |
| CSH 0.83–RT | 16.4 ± 2.1 | 78.3 ± 4.2 | 5.3 ± 2.1 | 12 | 1.08 |
| CSH 0.83–323 K | 12.1 ± 1.0 | 87.9 ± 2.0 | n.d. | 17 | 1.06 |
| CSH 0.83–353 K | 9.4 ± 1.0 | 80.2 ± 2.0 | 10.5 ± 1.0 | 21 | 1.05 |
| CSH 0.83–443 K | 11.0 ± 1.8 | 77.8 ± 3.6 | 11.1 ± 1.8 | 18 | 1.06 |
| CSH 1.0–323 K | 40.8 ± 5.3 | 59.2 ± 10.6 | n.d. | 5 | 1.20 |
| CSH 1.0–443 K | 26.0 ± 4.8 | 74.0 ± 9.6 | n.d. | 8 | 1.13 |
| CSH 1.4–323 K | 68.1 ± 3.8 | 32.0 ± 7.6 | n.d. | 3 | 1.34 |
| CSH 1.5–443 K | 39.5 ± 6.2 | 60.4 ± 12.4 | n.d. | 5 | 1.20 |
†
Maximum Ca/Si ratio that could be reached assuming that the charge originating from a vacant Si site is compensated for by interlayer Ca (Richardson, 2014 ▸).