Concrete Test Cylinder Calculator

How many strength test sets and cylinders a pour requires, and whether the results that came back satisfy the acceptance criteria.

ACI 318-08BNBC 2020

Save calculationFree account — your numbers come with you.

Code

Testing rules

The pour

Element

VolumeVyd³Days of placing

Surface areaAft²

The code counts each day's placing on its own; over several days the totals give the least it can need. Use Day by day for the exact count.

Cylinders cast per set

Specified strength

Compressive strengthf′cpsi

Everything you have entered is in the address bar, so the link reproduces this exact calculation.

Not met — average of tests 2–4, 7–9 below f′c

No single test is below the floor, so no investigation: take steps to raise the average of later tests (ACI 318-08 §5.6.3.4). The concrete placed is not rejected.

Test sets required

Cylinders to cast

Minimum single test

3500 psi

Lowest test

3650 psi

Cylinder strengths

psi

One row per strength test: the cylinders from one sample, at least two 6 × 12 in (150 × 300 mm) or three 4 × 8 in (100 × 200 mm).

Test	1	2	3	Avg
1				4167
2				3883
3				4283
4				3750
5				4450
6				4117
7				3650
8				4250
9				4017
10				4417

Design checks

Check	Demand	Capacity	DCR	Status
Test 1 — individual strength	3500 psi	4167 psi	0.840	✓ OK
Test 2 — individual strength	3500 psi	3883 psi	0.901	✓ OK
Test 3 — individual strength	3500 psi	4283 psi	0.817	✓ OK
Tests 1–3 — running average	4000 psi	4111 psi	0.973	✓ OK
Test 4 — individual strength	3500 psi	3750 psi	0.933	✓ OK
Tests 2–4 — running average	4000 psi	3972 psi	1.007	✗ FAIL
Test 5 — individual strength	3500 psi	4450 psi	0.787	✓ OK
Tests 3–5 — running average	4000 psi	4161 psi	0.961	✓ OK
Test 6 — individual strength	3500 psi	4117 psi	0.850	✓ OK
Tests 4–6 — running average	4000 psi	4106 psi	0.974	✓ OK
Test 7 — individual strength	3500 psi	3650 psi	0.959	✓ OK
Tests 5–7 — running average	4000 psi	4072 psi	0.982	✓ OK
Test 8 — individual strength	3500 psi	4250 psi	0.824	✓ OK
Tests 6–8 — running average	4000 psi	4006 psi	0.999	✓ OK
Test 9 — individual strength	3500 psi	4017 psi	0.871	✓ OK
Tests 7–9 — running average	4000 psi	3972 psi	1.007	✗ FAIL
Test 10 — individual strength	3500 psi	4417 psi	0.792	✓ OK
Tests 8–10 — running average	4000 psi	4228 psi	0.946	✓ OK

Calculation

1Sets required by pour daysACI318 5.6.2
$n_{time} = \text{one set per day of placing}$
$n_{time} = 3 \text{ days} \Rightarrow 3$
$n_{time}$ 3
2Sets required by volume placedACI318 5.6.2
$n_{vol} = \left\lceil \frac{V}{V_{set}} \right\rceil$
$n_{vol} = \left\lceil \frac{400.0}{150} \right\rceil = 3$
$n_{vol}$ 3
3Sets required by surface areaACI318 5.6.2
$n_{area} = \left\lceil \frac{A}{A_{set}} \right\rceil$
$n_{area} = \left\lceil \frac{12000}{5000} \right\rceil = 3$
$n_{area}$ 3
A thin element can cover a large area on very little concrete, which the volume criterion alone would under-test.
4Governing number of test setsACI318 5.6.2
$n = \max\left(n_{time},\; n_{vol},\; n_{area}\right) \ge n_{min}$
$n = \max(3,\,3,\,3) = 3,\quad n_{min} = 5 \Rightarrow 5$
$n$ 5
The calculated criteria give 3; the ACI 318-08 minimum of 5 governs.
5Cylinders to cast
$N = n \times c$
$N = 5 \times 3 = 15$
$N$ 15
6Lower bound on an individual strength testACI318 5.6.3.3(b)
$f_{min} = f'_c - 500\ \text{psi}$
$f_{min} = 3500$
$f_{min}$ 3500 psi

Warnings

2 acceptance checks are not met. Steps are required to raise the average of the strength tests that follow — a mix or procedure change, not rejection of the concrete already placed.

Notes

The code counts each day's placing on its own, so over 3 days these totals give the least the pour can need: a day with more than 150 yd³ needs more than one set that day. Enter each day's volume for the exact count.

Assumptions

One concrete class and one mix design. A pour with more than one class is tested for each class separately.
A cylinder entered as zero is treated as not cast, and is left out of that test's average.
Cylinder strengths are the values reported by the testing laboratory, already corrected for any specimen size or capping requirement.

What this calculator does not check

Counts the tests a pour requires and checks the results that came back. It does not evaluate the mix design, and it does not set a required average strength for proportioning.
Does not carry out the investigation that a failing result triggers — no core strength evaluation, load test or structural analysis.
Testing frequency is the code minimum. A specification or a superintending engineer can require more, and often does.
Assumes the tests are in chronological order, because the running average is taken over consecutive tests.

Results are for preliminary sizing and educational use. They are not a design and must be reviewed, verified and sealed by a licensed or registered engineer before being used in construction.

concrete-test-cylinder v1.2.0 · ACI 318-08 · input c705f39e792c32f2