Flow Table Test

Concrete, Tests
Flow table test

Flow Table Test

The flow table test measures the consistence of fresh concrete by the spread produced after a moulded sample is jolted 15 times. It is useful for high and very high workability concrete that may give a collapse slump, but it is not the slump-flow test for self-compacting concrete.

This test was covered by BS 1881:105:1984. The current British and European method is BS EN 12350-5:2019. The result is the average of two perpendicular spread diameters, reported in millimetres.

Scope: EN 12350-5 is sensitive to flow values from about 340 mm to 620 mm. Outside that range, another consistence test may be more suitable. The method does not apply to self-compacting concrete, foamed concrete, no-fines concrete, or concrete with a declared maximum aggregate size greater than 63 mm.

Flow Table Test Apparatus

The principal apparatus is summarized below. Use calibrated equipment that complies with the adopted standard rather than dimensions taken from a sketch alone.

Item Principal requirement Purpose
Moving table top 700 ± 2 mm square; flat metal surface at least 2 mm thick; mass 16 ± 0.5 kg Receives the concrete and falls freely onto the lower stops.
Fall height 40 ± 1 mm at the centre line of the front edge Provides a repeatable jolt.
Hollow cone 200 ± 2 mm high; 200 ± 2 mm base diameter; 130 ± 2 mm top diameter Forms the initial concrete sample.
Tamping bar Hard material; square section, 40 ± 1 mm side; about 200 mm working length Lightly levels each of the two layers.
Other items Measuring tape, remixing tray, shovel or scoop, moist cloth, trowel and timer Sampling, preparation, timing and measurement.
Concrete flow table showing perpendicular spread diameters, cone dimensions and 40 mm table drop
Concrete flow-table setup and the two spread measurements. Original CEW diagram; not a substitute for the standard apparatus drawing.

Flow Table Test Procedure

  1. Obtain and remix the sample. Take a representative fresh-concrete sample in accordance with EN 12350-1, then remix it on a suitable tray before the test.
  2. Set the table. Place the flow table on a level, stable surface free from vibration or shock. Check that the top reaches the upper stop and falls freely with little bounce.
  3. Prepare the contact surfaces. Clean and dampen the table and cone immediately before testing. Do not leave free water on either surface.
  4. Fill the cone. Centre and hold the cone. Fill it evenly in two equal layers, lightly tamping each layer 10 times with the tamping bar.
  5. Strike off. Bring the second layer slightly above the top if needed, strike the concrete level with the cone, and remove spilled concrete from the table.
  6. Lift the cone. Wait 10 to 30 seconds after striking off. Raise the cone vertically and steadily over 1 to 3 seconds.
  7. Drop the table 15 times. Start within 10 seconds after lifting the cone. Stabilize the table, raise its top smoothly to the upper stop, and allow it to fall freely. Complete 15 cycles, taking 1 to 3 seconds for each cycle.
  8. Measure the spread. Measure the maximum spread in two directions, d1 and d2, parallel to the table edges and perpendicular to each other. Record each diameter to the nearest 10 mm.
  9. Inspect the concrete. Note whether the spread is approximately circular and cohesive. Record visible paste separation, coarse-aggregate separation, bleeding, or an unusual shape.
Safety: Fresh cementitious concrete is alkaline and can burn skin or eyes. Wear suitable gloves and eye protection, and follow the laboratory safety procedure.

Flow Value Formula and Checked Example

The concrete flow value is the arithmetic mean of the two perpendicular spread diameters:

Flow value, F = (d1 + d2) / 2
where F, d1 and d2 are in millimetres.

Example: The measured diameters are d1 = 570 mm and d2 = 550 mm.

F = (570 + 550) / 2 = 560 mm.

The arithmetic is dimensionally consistent because both inputs and the result are lengths. Report the result as 560 mm, then compare it with the specified flow class or target for that concrete.

How to Interpret the Result

A higher flow value means the concrete spread farther under the specified jolting action. It does not, by itself, prove adequate strength, durability, pumpability, or resistance to segregation. Acceptance must come from the project specification and the selected concrete standard.

The appearance of the spread is also useful. A roughly circular, uniform spread indicates better cohesion. A ring of cement paste, separated coarse aggregate, clear bleed water, or a strongly irregular spread warns that the mix or the test needs review. Record the observation instead of reporting only one number.

A laboratory investigation discussed in the original article found a linear relation between flow and slump for the materials tested. However, it used only one aggregate type and grading and did not represent site conditions.

It would therefore be unwise to view slump and flow as generally interchangeable. Aggregate shape, grading and fines content can change the relationship.

For practical purposes, an appropriate test should be adopted. Such a test makes it possible to recognize a departure from the specified mix proportions, and this is what matters on site.

Concrete Flow Table, Slump-Flow and Mortar Flow Are Different

Method Material and movement Reported result Use
EN 12350-5 flow table Fresh concrete; two tamped layers; 15 table drops Average spread diameter, mm High-workability concrete, normally within about 340-620 mm flow
Slump test Fresh concrete; slump cone; no table drops Vertical slump, mm General consistence control where a valid slump is obtained
EN 12350-8 or ASTM C1611 slump-flow Self-compacting concrete; cone lifted without tamping or jolting Average spread diameter; time may also be recorded Unconfined flow of SCC
ASTM C1437 mortar flow Hydraulic-cement mortar on the ASTM C230/C230M circular table Flow increase using the method required by the mortar test Mortar and cement test procedures, not coarse-aggregate concrete
Compaction factor Concrete falls through hoppers into a cylinder Partially compacted density / fully compacted density Low-workability concrete where slump is not sensitive

For the broader meaning and factors that control fresh concrete, see workability of concrete. For a low-workability method, see the compaction factor test procedure and formula.

What Should Be Included in the Test Report?

  • Sample identification, location, date and time.
  • Standard and test method used.
  • Both measured diameters and the calculated flow value.
  • Specified flow class or target value, when applicable.
  • Any indication of segregation, bleeding or an abnormal spread.
  • Any departure from the standard procedure.
  • Test time relative to mixing when flow retention or comparisons over time matter.

Common Errors and Limitations

  • Excess water left on the table changes the contact condition.
  • A sloping, flexible or vibrating support changes the spread.
  • Hard contact with the upper stop or table bounce changes the applied energy.
  • Late cone removal or delayed jolting makes results less comparable.
  • Using mortar dimensions, SCC slump-flow rules, or an unrelated percentage formula gives a different test.
  • One flow number cannot be converted reliably to one slump value for all mixtures.

References