Concrete · Materials & serviceability
Concrete NDT: ultrasonic pulse velocity and crack depth calculator
Pulse velocity through the member and its quality grade, dynamic modulus, and the depth of a surface crack from transit times with and without the crack between the transducers.
Standard: AS 1012.24 / BS EN 12504-4 · quality grading (IS 13311-1) · surface crack depth by timing
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Path length | 300 | mm |
| Transit time | 71.4 | μs |
| Density | 2400 | kg/m³ |
| Dynamic Poisson's ratio | 0.2 | |
| Transducer offset each side of crack | 100 | mm |
| Surface transit time over sound concrete (2x) | 47.6 | μs |
| Transit time across the crack | 61 | μs |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Quality grade | good | |
| Dynamic modulus ρV²(1 + ν)(1 − 2ν)/(1 − ν) | 38.13 | GPa |
| Crack depth x√(tc²/ts² − 1) | 80.14 | mm |
| Limit: velocity for 'good' | 3.50 | km/s |
| Pulse velocity L/t | 4.20 | km/s |
- ✓ Pulse velocity ≥ 3.5 km/s (good or better)
Method, formulas and assumptions
- Quality grade = IF(300/71.4>4.5,"excellent",IF(300/71.4>=3.5,"good",IF(300/71.4>=3,"medium","doubtful"))) = good
- Dynamic modulus ρV²(1 + ν)(1 − 2ν)/(1 − ν) = 2400*(300/71.4*1000)^2*(1+0.2)*(1-2*0.2)/(1-0.2)/1E9 = 38.133 GPa
- Crack depth x√(tc²/ts² − 1) = 100*SQRT(MAX(0,61^2/47.6^2-1)) = 80.142 mm
- Limit: velocity for 'good' = 3.5 = 3.5 km/s
- Pulse velocity L/t = 300/71.4 = 4.2017 km/s
- Reinforcement parallel to the path and moisture raise UPV; calibrate on cores before inferring strength.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.