Vee-Bee Consistometer Test: Apparatus, Procedure and Interpretation
What is the Vee-Bee Test?
The Vee-Bee Consistometer Test (also written as VeBe test) is a workability test designed specifically for very low workability, stiff concrete mixes — the type used in road pavements, precast elements under pressure, and dry-lean concrete. In these mixes, the slump test gives zero slump and the compaction factor may be at the borderline of its sensitivity range.
The name “Vee-Bee” comes from the Swedish engineer V.B. (Viktor Bahrner) who developed it. The test measures the time in seconds required for fresh concrete, subject to vibration, to transform from a slump-cone shape to a remoulded flat circular shape. This time is called the Vee-Bee time (in seconds).
The test simulates actual compaction conditions more realistically than the slump test because vibration — which is the actual compaction method for most concrete — is used. A longer Vee-Bee time = more energy required = stiffer (lower workability) concrete.
In India, the test is included in IS 1199:1959. It is widely used for concrete mix design for highway and airport pavement concrete.
Apparatus Description
The Vee-Bee Consistometer consists of the following components:
1. Vibrating Table
A flat steel table mounted on springs that vibrates at a standard frequency. The vibration parameters as per the standard: frequency = 50 Hz (50 vibrations per second), amplitude = 0.35 mm (some sources state 0.5 mm). This standardized vibration mimics the action of a needle vibrator in the field.
2. Cylindrical Container
A steel cylinder with: Diameter = 240 mm, Height = 200 mm. This container sits on the vibrating table and holds the concrete.
3. Slump Cone
The standard slump cone (100 mm top, 200 mm bottom, 300 mm height — same as IS 1199 slump cone) is placed inside the cylindrical container to shape the fresh concrete before the vibration test begins.
4. Transparent (Glass) Disc / Rider
A transparent circular disc that is attached to a swiveling arm. After the slump cone is removed, this disc is lowered onto the slumped concrete surface. As vibration proceeds, the concrete flows outward and the disc settles down uniformly when the concrete becomes flat and level. This uniform contact of the disc with the concrete marks the end point of the test.
5. Swiveling Arm and Stopwatch
The arm positions the disc over the concrete. A stopwatch is used to measure the time from start of vibration to when the concrete surface is fully covered by the disc.
Test Procedure
- Place the cylindrical container on the vibrating table and fix it securely. Place the slump cone (open end down) inside the container.
- Fill the slump cone with concrete in three layers, rod each layer 25 times (same as standard slump test procedure).
- Remove the slump cone carefully by lifting it vertically. The concrete retains the frustum shape (it may slump slightly).
- Swing the transparent disc into position above the concrete and lower it gently onto the surface of the slumped concrete.
- Switch on the vibrator and simultaneously start the stopwatch.
- Observe the concrete as it becomes remoulded and flows outward under vibration, filling the cylindrical container.
- Stop the stopwatch when the transparent disc is completely and uniformly covered by cement slurry — i.e., when the concrete surface is completely flat and in full contact with the disc all around its area.
- The time recorded in seconds is the Vee-Bee time (VB seconds).
Result: Vee-Bee Seconds
The result of the test is expressed in seconds. A higher number of seconds = stiffer concrete = lower workability. The relationship is inverse: more workable concrete remoulds quickly under vibration (low VB seconds), while stiff concrete takes longer (high VB seconds).
Typical range for practical concrete mixes: 3–30 seconds. Values above 30 seconds indicate extremely stiff mixes rarely used in normal construction.
Interpretation and Typical Values
| Vee-Bee Time (seconds) | Degree of Workability | Approximate CF | Application |
|---|---|---|---|
| >20 | Extremely Low | <0.75 | Dry lean concrete, roller-compacted |
| 10–20 | Very Low | 0.75–0.80 | Road pavements, precast dry press |
| 5–10 | Low | 0.80–0.85 | Mass concrete, lightly reinforced |
| 3–5 | Medium | 0.85–0.92 | Normal RCC |
| 0–3 | High | >0.92 | Dense reinforcement sections |
Comparison: Vee-Bee vs Slump vs CF Test
| Feature | Slump Test | CF Test | Vee-Bee Test |
|---|---|---|---|
| Best for | Medium–High WB | Low–Medium WB | Very Low WB |
| Measurement | mm (slump) | Dimensionless ratio | Seconds (time) |
| Uses vibration | No | No | Yes |
| Simulates field | Partially | Partially | Best (vibration used) |
| Portability | High | Medium | Low (heavy equipment) |
🎯 Exam Tips (RTMNU)
- Vee-Bee test is best for very low workability mixes (road pavements, dry lean) — always state this application context.
- Cylindrical container: Ø 240 mm × 200 mm height; Vibration: 50 Hz frequency — memorize these values.
- End point: disc completely covered by cement slurry uniformly — be precise about this observation in procedure questions.
- Result is in SECONDS (higher = stiffer); CF is dimensionless ratio; Slump is in mm — know the units for all three tests.
- Key advantage over slump: uses vibration (same as field compaction method) — most realistic simulation.
- VB time 10–20 sec = very low workability = road pavement concrete — link the number to the application.
✅ Key Takeaways
- Vee-Bee test: for very low workability stiff mixes (road, precast, dry lean).
- Apparatus: vibrating table (50 Hz), cylindrical container (Ø240×200 mm), slump cone, transparent disc.
- Result in seconds: VB time 3–5 sec (medium), 10–20 sec (very low), >20 sec (extremely low).
- End point: uniform cement slurry contact over entire surface of transparent disc.
- Most realistic test — uses vibration like field compaction methods.
- Governed by IS 1199:1959.
📖 Related Reading: Compaction Factor Test | Flow Table Test for Concrete
🔗 External Reference: IS 1199:1959 – Methods of Sampling and Analysis of Concrete (BIS)
❓ FAQs
Q1. What type of concrete is the Vee-Bee test best suited for?
The Vee-Bee test is best suited for very low workability concrete mixes — road and airport pavement concrete, precast products, dry lean concrete, and roller-compacted concrete — where slump is zero or near zero and the slump test cannot discriminate between different mixes.
Q2. What is the end point of the Vee-Bee test?
The test ends when the transparent (glass) disc, placed on the top of the slumped concrete, is completely and uniformly covered by cement slurry all around its surface. This indicates the concrete has been fully remoulded and leveled under vibration.
Q3. What is the vibration frequency used in the Vee-Bee test?
The vibrating table in the Vee-Bee apparatus operates at a frequency of 50 Hz (50 vibrations per second) with an amplitude of 0.35 mm. This standardized vibration condition simulates field vibration and ensures reproducible results.
Q4. How does the Vee-Bee test differ from the slump test?
The slump test measures geometric subsidence (in mm) of concrete under gravity alone. The Vee-Bee test measures the time (in seconds) required for concrete to be remoulded flat under standardized vibration. The Vee-Bee test uses vibration (like actual field compaction), is more sensitive for stiff mixes, and gives a more realistic measure of compactibility.
Q5. What is a typical Vee-Bee time for road pavement concrete?
Road pavement concrete is classified as very low workability, corresponding to a Vee-Bee time of approximately 10–20 seconds. Normal RCC concrete used with mechanical vibrators has a Vee-Bee time of approximately 3–5 seconds.