The flow table test of concrete measures the workability and consistency of fresh concrete by checking how far it spreads on a flow table after controlled jolting. It is especially useful for concrete mixes that are too workable for a normal slump test or where flow behaviour is important for placement. The test helps identify whether concrete can flow properly without excessive segregation or bleeding. This blog explains the flow table test purpose, apparatus, step-by-step procedure, formula, result interpretation, advantages, limitations, and practical site precautions.
Quick Summary
The flow table test of concrete checks fresh concrete workability by measuring the spread diameter after the concrete is placed in a cone and jolted on a flow table. The flow percentage is calculated from the increase in diameter. Higher flow indicates higher workability, but very high flow may suggest segregation risk.
What Is the Flow Table Test of Concrete?
The flow table test of concrete is a fresh concrete test that measures the spread of concrete on a flat table after a standard number of drops or jolts. The concrete is first placed in a cone-shaped mould. After the mould is lifted, the table is dropped repeatedly from a fixed height. The concrete spreads, and the final spread diameter is measured.
The result indicates the flowability or consistency of concrete. The European flow table test is used for concrete consistency and is considered suitable for concrete with flow values between 340 mm and 620 mm. (YouTube)
In India, concrete consistency tests are covered under IS 1199 provisions for sampling, testing, and analysis of fresh concrete. Older references to IS 1199:1959 include flow table testing for concrete where the nominal maximum aggregate size does not exceed 38 mm. (Internet Archive)
Purpose of Flow Table Test
The main purpose of the flow table test is to measure the workability of fresh concrete. It shows how easily concrete can spread when subjected to movement.
The test is useful for checking:
- Concrete flowability
- Consistency of fresh concrete
- Suitability for placement
- Mix uniformity
- Risk of segregation
- Effect of water-cement ratio
- Effect of admixtures
- Quality control at site or lab
The test is commonly used for high-workability mixes and concrete that may not be properly assessed by a standard slump test.
Apparatus Required for Flow Table Test
The flow table test requires simple but standardised equipment.
Common apparatus includes:
- Flow table with hinged top
- Mould or flow cone
- Tamping rod
- Trowel
- Measuring scale or tape
- Scoop
- Clean water
- Damp cloth
- Fresh concrete sample
The equipment dimensions and procedure may vary depending on the standard followed, such as IS, EN, or project specifications. ASTM C1437 is a related standard used for determining the flow of hydraulic cement mortars, not normal concrete, so the correct concrete standard should be followed for site concrete testing. (ASTM International)
Principle of the Flow Table Test
The test works on a simple principle. Fresh concrete is placed in a standard mould and then allowed to spread after the mould is removed. The flow table is then raised and dropped a set number of times.
The more workable the concrete, the more it spreads. The less workable the concrete, the smaller the spread diameter.
However, flow does not mean quality by itself. A mix with very high flow may still be poor if it segregates, bleeds, or loses cement paste. That is why the result should be checked along with visual observation.
Flow Table Test Procedure
The exact procedure should follow the relevant project standard. A general procedure is given below for understanding.
Step 1: Prepare the Apparatus
Clean the flow table, mould, and tools. Remove old concrete, dust, oil, or loose particles. Dampen the table surface and mould lightly before testing, but do not leave standing water.
Step 2: Place the Mould
Place the flow cone at the centre of the flow table. Hold it firmly so it does not move while filling.
Step 3: Fill the Concrete
Fill the mould with fresh concrete in layers as required by the test standard. Compact each layer using the tamping rod as specified. Avoid over-tamping because it can affect the result.
Step 4: Level the Surface
Strike off the top surface with a trowel so the concrete is level with the mould. Clean any concrete spilled around the mould.
Step 5: Lift the Mould
Lift the mould vertically and steadily. Avoid twisting, shaking, or dragging the mould because this can disturb the concrete spread.
Step 6: Operate the Flow Table
Raise and drop the flow table the required number of times at the specified rate. The jolting action causes the concrete to spread outward.
Step 7: Measure the Spread
Measure the final spread of concrete in two directions at right angles. Take the average of the two readings as the final flow diameter.
Step 8: Observe the Concrete
Check whether the concrete spread is uniform. Look for segregation, bleeding, paste separation, or coarse aggregate collecting at the edges.
Flow Table Test Formula
The flow value is commonly expressed as a percentage increase in diameter.
Flow percentage = [(Final average diameter − Original base diameter) / Original base diameter] × 100
Where:
- Final average diameter = average spread of concrete after table drops
- Original base diameter = original bottom diameter of the mould
- Flow percentage = increase in spread expressed as a percentage
Example Calculation
If the original base diameter of the mould is 250 mm and the final average spread is 500 mm:
Flow percentage = [(500 − 250) / 250] × 100
Flow percentage = 100%
This means the concrete spread increased by 100% compared with the original mould base diameter.
How to Interpret Flow Table Test Results
A higher flow value means higher workability. A lower flow value means the concrete is stiffer and less workable.
However, the result must be judged with the mix design and placement requirement. Concrete for heavily reinforced sections may need higher workability. Concrete for sloped work or certain pavements may need lower workability.
|
Observation |
Possible Meaning |
|
Low spread |
Mix may be stiff or low in workability |
|
Moderate spread |
Mix may be suitable for normal placement |
|
High uniform spread |
Mix may have high workability |
|
Very high spread with paste separation |
Possible segregation risk |
|
Water collecting on surface |
Possible bleeding or excess water |
|
Coarse aggregate separated at edge |
Poor cohesion or segregation |
A good flow result should show both adequate spread and mix stability.
Flow Table Test vs Slump Test
The flow table test and slump test both measure fresh concrete workability, but they are not the same.
|
Factor |
Flow Table Test |
Slump Test |
|
Main result |
Spread diameter or flow percentage |
Vertical settlement or slump |
|
Best for |
High-workability concrete |
Normal workability concrete |
|
Measurement |
Horizontal flow |
Vertical drop |
|
Segregation observation |
Easier to observe spread pattern |
Visible but less detailed |
|
Site use |
Lab and selected site use |
Very common site test |
|
Limitation |
Needs flow table apparatus |
Less suitable for very fluid mixes |
The slump test is common for normal concrete. The flow table test is more useful when the concrete is highly workable or when spread behaviour matters.
Uses of Flow Table Test of Concrete
The flow table test of concrete is useful in several construction situations.
High-Workability Concrete
Concrete mixes with high workability may collapse in a slump test. The flow table test gives a better view of how the concrete spreads.
Quality Control
The test helps check whether fresh concrete matches the required consistency before placement.
Mix Design Trials
During trial mixes, engineers use workability tests to adjust water content, admixture dosage, aggregate grading, and cementitious materials.
Concrete with Admixtures
Plasticizers and superplasticizers improve flow. The flow table test helps observe the effect of these admixtures on workability and cohesion.
Precast and Special Concrete
The test may be useful where concrete must spread well into moulds or around reinforcement without leaving voids.
Advantages of Flow Table Test
The flow table test has several practical advantages.
- Measures flowability of fresh concrete
- Useful for highly workable mixes
- Helps identify segregation tendency
- Simple result based on spread diameter
- Useful in mix design comparisons
- Helps check consistency between batches
- Gives visual information about cohesion
- Supports site and laboratory quality control
The test is especially helpful when ordinary slump results do not describe the concrete behaviour clearly.
Limitations of Flow Table Test
The flow table test also has limitations.
- Not suitable for all concrete mixes
- Needs specific apparatus
- Result depends on correct procedure
- Not a direct strength test
- Can be affected by improper compaction
- Requires representative concrete sampling
- Very dry mixes may not spread meaningfully
- Result should not be used alone for approval
The test measures workability, not compressive strength. A concrete mix with good flow still needs proper design, placing, compaction, curing, and strength testing.
Factors Affecting Flow Table Test Results
Several factors can change the flow value.
Water Content
More water increases flow, but excess water can reduce strength and cause bleeding. Water should not be added casually at site to improve flow.
Admixtures
Superplasticizers can increase flow without adding extra water. However, dosage should follow mix design and manufacturer guidance.
Aggregate Shape and Grading
Rounded aggregates usually improve flow, while angular or poorly graded aggregates may reduce workability.
Cement Paste Content
A mix with enough paste can flow better and remain cohesive. Too little paste may cause harshness and poor finishing.
Temperature
Hot weather can reduce workability quickly because water evaporates faster and concrete sets sooner.
Time After Mixing
Concrete loses workability with time. Testing should be done within the specified time after sampling.
Common Mistakes During Flow Table Test
Incorrect testing can give misleading results. Avoid these mistakes:
- Using a dirty or dry flow table
- Not placing the mould at the centre
- Over-compacting or under-compacting concrete
- Lifting the mould unevenly
- Dropping the table at the wrong rate
- Measuring only one diameter
- Ignoring segregation or bleeding
- Testing a non-representative sample
- Adding water before testing without approval
- Comparing results from different standards
The test should be performed consistently to compare results accurately.
Field Quality Checks After the Test
After measuring the flow, observe the concrete carefully. The spread should be reasonably circular and uniform. The paste should not run separately from aggregates. There should not be excessive water on the surface.
If the concrete segregates, the mix may need correction. If the flow is too low, placement and compaction may be difficult. Any adjustment should be made through approved mix design changes, not by random water addition.
When Should the Flow Table Test Be Used?
Use the flow table test when concrete workability needs to be assessed by spread rather than slump. It is useful for high-workability mixes, trial mixes, and concrete where flow around reinforcement is important.
For normal residential concrete, slump testing is often more common. However, the flow table test may be used when specified by the engineer, quality control plan, or project standard.
Conclusion
The flow table test of concrete is a useful method for checking the workability and flow behaviour of fresh concrete. It measures how far concrete spreads after controlled table movement and helps identify whether the mix is too stiff, workable, or at risk of segregation. The test is helpful for high-workability mixes, trial mixes, and quality control. For accurate results, follow the relevant standard, use clean apparatus, take representative samples, and interpret flow along with visual stability.
FAQs
- What is the flow table test of concrete?
The flow table test of concrete is a fresh concrete workability test that measures how far concrete spreads on a flow table after controlled drops. It helps evaluate concrete consistency, flowability, and stability before placement. - Why is the flow table test done?
The flow table test is done to check whether fresh concrete has suitable workability for placement and compaction. It is useful for high-workability concrete, mix design trials, and quality control where slump results may not fully show flow behaviour. - What is the formula for flow percentage?
The flow percentage formula is: [(Final average diameter − Original base diameter) / Original base diameter] × 100. The final average diameter is measured after the concrete spreads on the flow table. - What does a high flow value mean?
A high flow value means the concrete has higher workability and spreads more easily. However, very high flow with paste separation, bleeding, or aggregate movement may indicate segregation risk. The spread should be judged with visual stability. - What equipment is used for the flow table test?
The equipment includes a flow table, flow cone or mould, tamping rod, trowel, scoop, measuring scale, water, damp cloth, and fresh concrete sample. The exact apparatus dimensions depend on the standard followed for the test. - What is the difference between slump test and flow table test?
The slump test measures vertical settlement of concrete, while the flow table test measures horizontal spread. Slump testing is common for normal workability concrete, while the flow table test is useful for highly workable or flowing concrete. - Is the flow table test a strength test?
No, the flow table test is not a strength test. It measures fresh concrete workability and consistency. Concrete strength must be checked separately through cube or cylinder compression tests as per the project specification. - What are common errors in the flow table test?
Common errors include using dirty equipment, wrong compaction, uneven cone lifting, incorrect table dropping, poor sampling, measuring only one direction, and ignoring segregation. These mistakes can make the flow result unreliable.
Sowjanya Siddanoor