Research Article
Ultrasonic Time-Frequency Response Characteristics for Damage Evolution of Back-Filling Concrete under Staged Loading Conditions
Table 1
.Composition of the concrete mix.
| Component type | Dosage |
| P. O42.5 | 850 kg | Sand (0 ∼ 5 mm) | 700 kg | Gravel (5 ∼ 15 mm) | 850 kg | Water | 325 kg | Admixtures (waterproofing agent) | 1.3 kg | W/C ratio | 0.38 |
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