Concrete QC — Within-Test Variability (COV)
Within-Test Variability (COV) for concrete quality control and investigation work.
When two companion cylinders disagree by 15%, the lab — not the pour — is the prime suspect: bad caps, unground ends and misaligned platens all read LOW. ASTM C39's precision statement makes scatter an objective question; this check applies it before anyone schedules cores.
Formula
Note: Planning estimate only — strength for structural decisions (formwork striking, post-tensioning, loading) must be verified by site-cured specimens or a calibrated maturity system per the project specification.
Within-Test Variability (COV) for concrete quality control and investigation work. A free concrete curing, maturity & strength tool — no sign-up, no upload, instant results in your browser.
About Concrete QC — Within-Test Variability (COV)
Concrete QC — Within-Test Variability (COV) computes the governing relationship range % = (max − min)/mean × 100, vs ASTM C39 precision limits live as you type. When two companion cylinders disagree by 15%, the lab — not the pour — is the prime suspect: bad caps, unground ends and misaligned platens all read LOW. ASTM C39's precision statement makes scatter an objective question; this check applies it before anyone schedules cores. Defaults are pre-filled with realistic values for this exact scenario, and the worked example substitutes your numbers step by step so the math is never a black box.
How to use Concrete QC — Within-Test Variability (COV)
- 1Enter your values — Cylinder A, Cylinder B, Cylinder C (0 if pair) (sensible defaults are pre-filled).
- 2Read the live results: Mean, Range as % of mean.
- 3Check the "with your numbers" line to see range % = (max − min)/mean × 100, vs ASTM C39 precision limits substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Concrete QC — Within-Test Variability (COV)?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula range % = (max − min)/mean × 100, vs ASTM C39 precision limits with authoritative sources cited on the page (ACI 318 / ASTM C39, C42, C496, C597; IS 456:2000 — Plain and reinforced concrete code of practice; Neville, A.M., Properties of Concrete, 5th ed.)
- ✓When two companion cylinders disagree by 15%, the lab — not the pour — is the prime suspect: bad caps, unground ends and misaligned platens all read LOW.
- ✓Niche-specific defaults give a meaningful worked answer the moment the page loads
Frequently asked questions
What formula does the concrete qc — within-test variability (cov) use?+
It evaluates range % = (max − min)/mean × 100, vs ASTM C39 precision limits, exactly as published. Sources: ACI 318 / ASTM C39, C42, C496, C597; IS 456:2000 — Plain and reinforced concrete code of practice; Neville, A.M., Properties of Concrete, 5th ed.. The substituted worked example on the page lets you verify every step against the textbook.
How should I read the result — and how far can I trust it?+
When two companion cylinders disagree by 15%, the lab — not the pour — is the prime suspect: bad caps, unground ends and misaligned platens all read LOW. Planning estimate only — strength for structural decisions (formwork striking, post-tensioning, loading) must be verified by site-cured specimens or a calibrated maturity system per the project specification.
When is this calculator the right tool for the job?+
Within-Test Variability (COV) for concrete quality control and investigation work. A free concrete curing, maturity & strength tool. ASTM C39's precision statement makes scatter an objective question; this check applies it before anyone schedules cores. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Do I need to install anything or create an account?+
No. The tool is pure client-side JavaScript: open the page and it works, offline once loaded, with no account, no quota and no data leaving your device.
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