Concrete QC — Acceptance Check (ACI 318)
Acceptance Check (ACI 318) for concrete quality control and investigation work.
ACI's two-armed test is widely misquoted: ONE low cylinder doesn't fail a pour unless it breaches f'c − 3.5 MPa, and the average arm uses consecutive tests. Knowing the actual criterion turns many panicked Friday phone calls into routine documentation.
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.
Acceptance Check (ACI 318) 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 — Acceptance Check (ACI 318)
Concrete QC — Acceptance Check (ACI 318) computes the governing relationship Accept if: average of 3 ≥ f'c AND no individual < f'c − 3.5 MPa (500 psi) live as you type. ACI's two-armed test is widely misquoted: ONE low cylinder doesn't fail a pour unless it breaches f'c − 3.5 MPa, and the average arm uses consecutive tests. Knowing the actual criterion turns many panicked Friday phone calls into routine documentation. 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 — Acceptance Check (ACI 318)
- 1Enter your values — Cylinder 1, Cylinder 2, Cylinder 3, Specified f'c (sensible defaults are pre-filled).
- 2Read the live results: Test average, Worst-case margin vs f'c−3.5.
- 3Check the "with your numbers" line to see Accept if: average of 3 ≥ f'c AND no individual < f'c − 3.5 MPa (500 psi) substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use Concrete QC — Acceptance Check (ACI 318)?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula Accept if: average of 3 ≥ f'c AND no individual < f'c − 3.5 MPa (500 psi) 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.)
- ✓ACI's two-armed test is widely misquoted: ONE low cylinder doesn't fail a pour unless it breaches f'c − 3.5 MPa, and the average arm uses consecutive tests.
- ✓SI ⇄ Imperial toggle converts your inputs in place, so you can work in the units your drawings use
Frequently asked questions
What formula does the concrete qc — acceptance check (aci 318) use?+
It evaluates Accept if: average of 3 ≥ f'c AND no individual < f'c − 3.5 MPa (500 psi), 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?+
ACI's two-armed test is widely misquoted: ONE low cylinder doesn't fail a pour unless it breaches f'c − 3.5 MPa, and the average arm uses consecutive tests. 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?+
Acceptance Check (ACI 318) for concrete quality control and investigation work. A free concrete curing, maturity & strength tool. Knowing the actual criterion turns many panicked Friday phone calls into routine documentation. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Does it support both metric and imperial units?+
Yes — the SI ⇄ Imperial toggle converts the values already in the fields, preserving the physical quantity, so you can flip mid-calculation without re-entering anything.
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