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Is there a relationship between concrete strength and wave speed? How can the acceptable minimum wave speed be determined?
Based on information reported in American Concrete Institute (ACI) 228.1, as well as in other codes and specifications, the concrete compressive strength is approximately proportional to compression wave velocity to the 4th power. This means, if σ is the concrete strength, W is the wave speed, and k1 and k2 are constants:
σ = k1 × W4 or W = k2× σ1/4
Those relationships can be used to compare the strength and wave speed of concretes with a similar mix. The following table might offer a rough guide:
| fc | wave speed | fc | wave speed |
| psi | ft/sec | MPa | m/sec |
| 2000 | 9,249 | 13.8 | 2,819 |
| 3000 | 10,235 | 20.7 | 3,120 |
| 4000 | 10,999 | 27.6 | 3,352 |
| 5000 | 11,630 | 34.5 | 3,545 |
| 6000 | 12,172 | 41.4 | 3,710 |
| 7000 | 12,650 | 48.3 | 3,856 |
| 8000 | 13,080 | 55.2 | 3,986 |
| 9000 | 13,470 | 62.1 | 4,106 |
| 10000 | 13,830 | 69.0 | 4,215 |
The minimum acceptable strength for the concrete of a drilled shaft project is σA. One of the drilled shafts associated with the project has a wave speed of WM, which is obtained by performing a Pile Integrity Test or Cross Hole Sonic Logging procedure. The measure of strength is σM. This measurement, for example, can be determined by extracting a cylinder. A relationship may be established for the minimum acceptable wave speed of other drilled shafts in the same project. WA is calculated as follows:
WA = WM (σA / σM)1/4