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Is that concrete cube test result actually a failure?
Check three-cube specimen consistency and explore the general four-result and qualifying small-pour acceptance checks under IS 456:2000 Table 11, as amended. A sample result is the average of three specimens—not a single cube reading.
Educational calculations only: This tool does not issue NABL test reports, certify compliance or establish structural safety. Verify the applicable edition, amendments, sampling frequency, test procedures, correct standard deviation and project specifications with the responsible engineer.
1. Enter concrete data
One row = one sample, with exactly 3 specimen strengths separated by commas. For the general case use complete blocks of 4 chronological samples. For the qualifying small-pour exception use 1–3 samples, only where fewer than 4 are required by the sampling schedule.
The calculations run locally in your browser. Values are not uploaded or stored.
2. Interpretation
Results will appear here.
An “illustrated checks satisfied” result is not a structural clearance or a substitute for the complete project acceptance assessment.
Request testing quotation ↗ GTSM website ↗3. What the calculation means
Three-cube sample validity: Under Clause 15.4, the test result of a sample is the mean of three specimens, provided no specimen deviates from that mean by more than ±15%. Invalid sample results must be investigated before any acceptance conclusion.
General four-result case: For grades M15 and above, the required mean of four non-overlapping consecutive valid sample results is at least fck + the greater of [0.825 × standard deviation, rounded to nearest 0.5 MPa] and 3 MPa. The required minimum for each valid sample result is fck − 3 MPa (IS 456 Table 11, as amended).
Small pour: For concrete quantity up to 30 m³ when fewer than four samples are required, the mean of the required sample results must be at least fck + 4 MPa; the individual minimum is fck − 2 MPa for 2–3 samples. Where exactly one sample is required, that sample itself must meet fck + 4 MPa. Do not select this option for a larger pour or an incomplete sample series.
Read the full technical explanation: M25 Cube Test Result 23 MPa: Pass or Fail?
About GTSM Testing Labs
GTSM Testing Labs LLP provides concrete cube testing, construction-material testing, geotechnical investigations and structural testing in Ahmedabad and across Gujarat. If you need testing for a current site, send us a quotation enquiry.
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