Concrete · Materials & serviceability
Concrete NDT: half-cell potential survey calculator
Converts readings to the copper/copper-sulfate scale and classifies each point: > −200 mV low (90 % no corrosion), −200 to −350 uncertain, < −350 mV high (90 % corrosion).
Standard: ASTM C876 · CSE thresholds −200 / −350 mV · electrode conversion SCE +75 mV, Ag/AgCl +119 mV vs CSE
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 |
|---|---|---|
| Reference electrode | Cu/CuSO₄ (CSE) | |
| Accept if high-risk points ≤ | 10 | % |
| Readings: grid point, potential (mV) | 1, -137 2, -128 3, -169 4, -191 5, -253 6, -300 7, -297 8, -379 9, -299 10, -236 11, -302 12, -194 13, -158 14, -143 15, -170 16, -147 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Electrode offset vs CSE | 0.000 | mV |
| Points | 16.00 | |
| Low risk | 9.00 | |
| Uncertain | 6.00 | |
| High risk | 1.00 | |
| Most negative (CSE) | -379.0 | mV |
| High-risk share | 6.25 | % |
- ✓ High-risk share ≤ limit
Method, formulas and assumptions
- Electrode offset vs CSE = CHOOSE(1,0,75,119) = 0 mV
- Points = COUNT([t.cse]) = 16
- Low risk = COUNTIF([t.cl],"=1") = 9
- Uncertain = COUNTIF([t.cl],"=2") = 6
- High risk = COUNTIF([t.cl],"=3") = 1
- Most negative (CSE) = MIN([t.cse]) = -379 mV
- High-risk share = 1/16*100 = 6.25 %
- Potentials indicate probability, not rate. Confirm with chloride profiles, carbonation depth, cover and breakouts; temperature and moisture shift readings.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.