A project required strict quality control for concrete works. The contractor engaged an accredited laboratory to test compressive strength of concrete cubes.
During an internal audit, inconsistencies were found in test results some concrete cubes passed strength requirements while others from the same batch failed.
This raised concerns:
- Was the concrete quality inconsistent?
- Or were the testing instruments unreliable?
The laboratory was accredited under ISO/IEC 17025:2017, so the following controls were in place:
1. Equipment Calibration (Clause 6.4) - The compression testing machine had valid calibration traceable to national standards. Calibration records showed it was within acceptable tolerance.
2. Measurement Traceability (Clause 6.5) - All measurements were linked to SI units, ensuring reliability and comparability.
3. Method Validation (Clause 7.2) - The lab followed a recognized standard (e.g., BS EN or ASTM) for concrete testing. Procedures were verified and controlled.
After investigation, the issue was not the lab, it was about poor sampling method at site and improper curing of test cubes before delivery to the lab
4. Competency of Personnel (Clause 6.2) - The technician conducting the test was certified and competent.
- The lab results were validated as accurate and reliable
- The contractor corrected site practices (sampling & curing)
- Confidence in test results was restored
ISO/IEC 17025:2017 ensures that:
- Laboratory results are technically valid
- Equipment is accurate and traceable
- Personnel are competent
So when results differ, the issue is often outside the lab, not the testing itself.






