| Year elapsed since installation (yr) | 1 | 2 | 3 | 9 | 16 | |
|---|---|---|---|---|---|---|
| Mean compressive strength (MPa) | Damaged | 23.4±1.6 | 24.9±0.9 | 24.4±2.6 | 20.6±2.3 | 20.3±1.5 |
| Undamaged | 24.8±4.7 | 25.5±3.5 | 23.4±2.8 | 21.5±5.5 | 21.1±4.2 | |
| Residual compressive strength ratio (%) | 94.6 | 97.6 | 104.0 | 95.6 | 96.3 | |