Flow Table Test for Concrete: Apparatus, Procedure and Flow Percentage
What is the Flow Table Test?
The Flow Table Test is a workability test designed for high and very high workability concrete mixes — those that would give collapse slump or flow too freely to be measured by the standard slump test. It is particularly suitable for:
- Flowing concrete and self-compacting concrete (SCC)
- Pumped concrete mixes with long delivery distances
- Concrete with high superplasticizer dosages
- Mortar workability testing in plastering and laying work
The test measures the percentage increase in diameter (called flow) of a concrete or mortar sample after being subjected to a fixed number of jolts (drops) of the flow table. More flow = more workable mix.
The test is governed by IS 1199:1959 (for concrete) and is also described in IS 4031 (for cement mortars). It is widely used in laboratory settings for mix design of flowing concretes.
Apparatus
Flow Table
A square steel table: 700 mm × 700 mm, hinged on one side to a fixed base. The table can be raised by 40 mm on one side and dropped to fall under its own weight — this constitutes one “jolt.” The table surface has concentric circles marked at specific diameters (200 mm, 300 mm, etc.) to aid in measuring the spread diameter.
Truncated Cone (Flow Cone)
- Top diameter: 70 mm
- Bottom diameter: 100 mm
- Height: 50 mm
- Solid, no trap door needed — simply lifted off.
Other Equipment
Tamping rod, measuring scale/calipers, damp cloth for the table surface.
Procedure
- Clean and dampen the surface of the flow table. Place the truncated cone (larger end down) at the centre of the table.
- Fill the cone in two layers, tamping each layer 10 times with the tamping rod. Strike off the top flush.
- Lift the cone vertically — the concrete spreads outward slightly under its own weight (initial spread).
- Raise the flow table by gripping the handle and lifting one side to the fixed stop (40 mm rise) and then releasing it to fall back. This constitutes one jolt (drop). Repeat for a total of 15 jolts at a rate of about one per second.
- After 15 jolts, measure the diameter of the spread concrete in two directions at right angles using a steel rule. Average the two readings to get D (in mm).
- Calculate the flow percentage.
Flow Percentage Calculation
Where:
D = Average spread diameter after 15 jolts (mm)
D₀ = Initial base diameter of the cone = 100 mm
Example: After 15 jolts, the concrete spreads to diameters of 275 mm and 285 mm in two perpendicular directions. Average D = (275 + 285) / 2 = 280 mm.
Flow % = [(280 – 100) / 100] × 100 = 180%
A flow of 180% indicates very high workability, suitable for pumped concrete or highly flowable mixes.
Interpretation of Results
| Flow % | Workability | Application |
|---|---|---|
| 0–50% | Low | Stiff concrete (better tested by CF/Vee-Bee) |
| 50–100% | Medium | Normal concrete, suitable range for flow test |
| 100–150% | High | Pumped concrete, high workability RCC |
| 150–200% | Very High | SCC, flowing concrete |
| >200% | Extremely High | May indicate segregation risk — review mix |
Applications
The flow table test is preferred over the slump test in the following situations:
- Ready-mix and pumped concrete: Where slump exceeds 175 mm (collapse region of slump test).
- SCC mix design: Flow table gives a more meaningful measure of flowability for initial SCC mix design (before fine-tuning with slump flow and other SCC-specific tests).
- Mortar workability: IS 4031 uses the flow table (with a smaller cone) to test the workability of cement mortars used for plastering and masonry.
- Laboratory mix design: More sensitive and reproducible than slump for very high workability mixes.
🎯 Exam Tips (RTMNU)
- Flow Table dimensions: 700×700 mm table; cone: top 70 mm, bottom 100 mm, height 50 mm — know these for 2-mark questions.
- 15 jolts (drops of 40 mm) — this specific number appears in procedure questions.
- Flow % formula: [(D – D₀)/D₀] × 100; D₀ = 100 mm — practice with numerical examples.
- Fill cone in TWO layers, 10 tamps each — distinguish from slump test (3 layers, 25 rods each).
- Flow table test = for HIGH workability (where slump test gives collapse/out-of-range results).
- Measuring diameter in TWO perpendicular directions and averaging — always mention this for procedural accuracy.
✅ Key Takeaways
- Flow Table Test: for high and very high workability concrete, flowing concrete, SCC.
- Table: 700×700 mm; Cone: 70/100/50 mm; 15 jolts of 40 mm drop.
- Flow % = [(D – D₀) / D₀] × 100; D₀ = 100 mm base diameter.
- Example: D = 280 mm → Flow = 180% (very high workability).
- Measure spread in two perpendicular directions; average for D.
- Governed by IS 1199:1959; also IS 4031 for mortars.
📖 Related Reading: Vee-Bee Consistometer Test | Segregation and Bleeding of Concrete
🔗 External Reference: IS 1199:1959 – Methods of Sampling and Analysis of Concrete (BIS)
❓ FAQs
Q1. When should the flow table test be used instead of the slump test?
The flow table test should be used when concrete has very high workability beyond the range of the slump test (collapse slump or near-collapse), such as for pumped concrete, self-compacting concrete, and other flowing mixes. It is also used for mortar workability testing.
Q2. How many jolts are given in the flow table test?
The flow table is raised 40 mm on one side and dropped (jolted) a total of 15 times at approximately one jolt per second. After these 15 jolts, the spread diameter of the concrete is measured.
Q3. What are the dimensions of the flow cone?
The truncated cone used in the flow table test has: top diameter = 70 mm, bottom diameter = 100 mm, and height = 50 mm. Note that the base diameter D₀ = 100 mm is used in the flow percentage formula.
Q4. What flow percentage is considered suitable for SCC?
For self-compacting concrete assessed by flow table, a flow percentage of 150–200% is typically considered appropriate for good filling ability. Flow above 200% may indicate risk of segregation. For fine-tuned SCC testing, the Slump Flow Test (measuring spread in mm) is more commonly used.
Q5. How is the flow table test different from the slump test?
The slump test measures vertical subsidence (mm) of a 300 mm tall cone under gravity. The flow table test measures lateral spread (%) of a 50 mm tall cone after 15 standardized jolts. The flow table test is more suitable for high-workability and flowing mixes; the slump test works better for medium-workability structural concrete.