The slump flow test tells you how far self-compacting concrete spreads. The V-funnel test tells you something equally important: how fast it gets there. By timing how long a fixed volume of concrete takes to discharge through a narrow opening, the V-funnel gives a simple, practical index of the mix’s plastic viscosity and its filling ability.
If you are running SCC trial mixes or doing site quality control on SCC, this is one of the first tests you will reach for — it needs only a funnel, a bucket, and a stopwatch.
What the V-Funnel Test Measures
Self-compacting concrete has two fresh properties that matter before anything else: it must flow on its own (filling ability) and it must stay uniform while it flows (stability). The V-funnel flow time, recorded as tV in seconds, reflects both:
- Plastic viscosity. A longer flow time means the paste is more viscous — the concrete resists flow. A shorter time means a more fluid mix.
- Filling ability. The funnel’s narrow outlet restricts flow the way tight formwork does, so the discharge time indicates whether the mix will fill a mould without help.
- Segregation tendency (with the T5min repeat). Run the test, refill the funnel, wait 5 minutes, and run it again. If the second time is much longer, the aggregate has settled — the mix is segregating.
Practical note: The V-funnel does not give a true viscosity value in Pa·s. It gives an index of viscosity — a comparative number you can use to rank trial mixes and to check that site batches match the approved trial. Treat it as a quality-control tool, not a rheometer.
Governing Standard
The V-funnel test is covered by EN 12350-9:2010 — Testing fresh concrete, Part 9: Self-compacting concrete — V-funnel test. The principle and apparatus also come from the EFNARC Specification and Guidelines for Self-Compacting Concrete.
Standards correction: Some older write-ups cite ASTM C1611 for the V-funnel. That is wrong — ASTM C1611 is the slump flow test. There is no ASTM equivalent of the V-funnel; the correct reference is EN 12350-9.
The test is not suitable when the nominal maximum aggregate size exceeds 22.4 mm, because large aggregate can jam mechanically in the outlet and give a misleading time.
Apparatus
The V-funnel is a V-shaped metal funnel fitted with a quick-release, watertight gate at the bottom, mounted on a frame so the top stays horizontal. Key internal dimensions:
| Part | Dimension |
|---|---|
| Height of the V-section | 425 mm |
| Width at the top | 490 mm |
| Width at the bottom of the V | 65 mm |
| Thickness (depth of the funnel) | 75 mm |
| Rectangular discharge section below the V | 150 mm deep |
You will also need:
- A container (bucket) of at least 12 L capacity to catch the discharge
- A stopwatch reading to 0.1 s
- A straightedge to strike off the concrete level with the top
- A damp sponge or towel to moisten the funnel
Practical note: The inside of the funnel must be smooth and clean. Dried concrete stuck to the walls slows the discharge and ruins repeatability — clean it after every single run.
Test Procedure (EN 12350-9)
- Place the V-funnel upright on firm, level ground with the top horizontal and the gate closed.
- Moisten the inside surfaces with the damp sponge, then drain off surplus water through the gate — the surface should be just wet, not dripping.
- Close the gate and place the bucket underneath.
- Fill the funnel completely with a representative sample of fresh SCC in one go — no tamping, no rodding, no vibration.
- Strike off the surplus with the straightedge so the concrete is level with the top.
- Wait (10 ± 2) seconds, then open the gate and start the stopwatch at the same instant.
- Watch from above and stop the watch the moment you can see clear space (daylight) through the outlet. Record this as the V-funnel flow time tV, to the nearest 0.1 s.
The T5min repeat (segregation check)
For an indication of segregation resistance, refill the funnel immediately after the first run (do not clean or re-moisten it), close the gate, and let the concrete rest for 5 minutes. Then open the gate and record the second flow time, tV,5min. EFNARC’s older guidance treats an increase of more than about 3 seconds as a warning sign: the mix is settling and may segregate in the formwork.
Practical note: The whole test, from sampling to the final reading, should be finished within about 5 minutes of mixing where possible — SCC loses workability fast, especially in hot weather, and a delayed test will flatter a stiff mix.
V-Funnel Time Classes: VF1 and VF2
EFNARC (2005) classifies SCC viscosity using the V-funnel time together with the T500 time from the slump flow test:
| Class | V-funnel time tV | T500 (slump flow) | Typical use |
|---|---|---|---|
| VF1 / VS1 | ≤ 8 s | ≤ 2 s | Low-viscosity mixes — good filling ability even with congested reinforcement, but check stability |
| VF2 / VS2 | 9–25 s | > 2 s | Higher-viscosity mixes — better segregation resistance; suitable for most normal applications |
Shorter times mean greater flowability. Most general-purpose SCC falls in VF2; VF1 mixes are very fluid and need careful stability control (they are the ones most likely to segregate).
Interpreting the Results
| Observation | What it usually means | What to adjust |
|---|---|---|
| tV well below 8 s with visible bleeding | Mix too fluid; segregation risk | Reduce water or superplasticizer, add viscosity-modifying admixture |
| tV within the target class | Viscosity is where you want it | Confirm with slump flow and a passing-ability test |
| tV above 25 s | Mix too stiff or blocking in the outlet | Increase superplasticizer dosage, check aggregate grading |
| tV,5min − tV > 3 s | Segregation during rest | Increase paste viscosity or reduce coarse aggregate content |
| Flow stops and restarts in lumps | Aggregate arching at the outlet | Coarse aggregate too large or gap-graded; check max size ≤ 22.4 mm |
Practical note: A long V-funnel time on its own does not always mean a bad mix — VF2 is perfectly normal. Judge the time together with the slump flow spread and one passing-ability test (L-box or J-ring) before changing the mix.
Worked Example
A trial SCC batch (20 mm max aggregate, target class VF2) is tested in the lab:
- First run: gate opened 10 s after filling; clear space visible at tV = 11.5 s
- Refilled funnel, rested 5 minutes: tV,5min = 14.9 s
Interpretation:
- Viscosity class: 11.5 s falls in the 9–25 s band → VF2. The viscosity is in the normal range for general SCC work.
- Segregation check: increase = 14.9 − 11.5 = 3.4 s, just above the 3 s guideline → the mix is borderline. Before approving it, increase the paste viscosity slightly (a small VMA dose or a marginal water reduction) and retest. The discharge was also continuous with no lumps, which is a good sign.
How the V-Funnel Relates to the Other SCC Tests
No single test describes SCC fully. The standard fresh-concrete test battery is:
| Test | What it checks | Standard |
|---|---|---|
| Slump flow (+ T500) | Filling ability, spread | EN 12350-8 / ASTM C1611 |
| V-funnel | Viscosity, filling ability, segregation | EN 12350-9 |
| L-box | Passing ability through reinforcement | EN 12350-10 |
| J-ring | Passing ability, blocking step | EN 12350-12 / ASTM C1621 |
Run at least the slump flow with the V-funnel on every trial, and add the L-box or J-ring whenever the concrete must pass through reinforcement. For background on the material itself, see the self-compacting concrete introduction, and for the companion passing-ability tests, the L-box test, the J-ring test, and the slump flow test.
Frequently Asked Questions
What is a good V-funnel flow time for SCC?
For most work, 9–25 seconds (class VF2) is the target. Below 8 seconds (VF1) is very fluid — acceptable, but verify stability. Times above 25 seconds indicate an overly stiff mix or blocking.
What is the difference between the V-funnel test and the T5min test?
They use the same apparatus. The first run measures flow time (viscosity/filling ability); the repeat run after 5 minutes of rest measures segregation resistance by comparing the two times.
Can the V-funnel be used with 25 mm aggregate?
No. EN 12350-9 excludes mixes with maximum aggregate size above 22.4 mm — large particles can arch across the outlet and the time no longer reflects the concrete’s properties.
Is there an ASTM standard for the V-funnel test?
No. The V-funnel is an EN/EFNARC test (EN 12350-9). ASTM C1611 covers slump flow and ASTM C1621 covers the J-ring — neither is the V-funnel.
Why did the flow stop halfway and then restart?
That is usually aggregate arching at the narrow outlet or early segregation. Note it in the report — non-uniform flow is itself a result — and check the aggregate size and grading before retesting.
The V-funnel is one of the simplest SCC tests you can run, and one of the most informative: a single timed discharge tells you about viscosity, filling ability, and — with the 5-minute repeat — stability. Keep the funnel clean, respect the 22.4 mm aggregate limit, and always read the time together with the slump flow before judging a mix.
Written by Mohsin Raza Adil — BSc Civil Engineering Technologist (NTC-registered), Pakistan.
Mohsin Raza Adil
BSc Civil Engineering Technologist (NTC-registered), Pakistan. I write practical, field-tested guides on construction materials, soil testing and site engineering — the way it is actually done on site.
