| Aging period | |||||||||
| Samples | S0 | S1 | S2 | S3 | S4 | S5 | S6 | S7 | S8 |
| Wwp CW | 3.5 × 105 2.8 × 105 | 3 × 105 3.1 × 105 | 3.1 × 105 2.8 × 105 | 2.5 × 105 2.5 × 105 | 2.2 × 105 2.5 × 105 | 2 × 105 2.1 × 105 | 2.3 × 105 1.5 × 105 | 1.9 × 105 1.6 × 105 | 1.4 × 105 1.5 × 105 |