Vee-Bee consistency test | Workability of Concrete Test | Concrete test

Vee-Bee consistency test

In this article, we explained how to determine the workability of freshly mixed concrete by the Vee-Bee consistency test.

 

Theory and Scope of the test

Like other tests, this test only measures a specific aspect of performance; Provides an indication of test motion and the compactness of freshly mixed concrete. It measures the comparative effort required to transfer the mass of concrete by vibration from one definite shape to another, i.e. from conical shape to cylindrical). The amount of effort known as the remoulding effort is expressed in seconds over time. This time required to completely redesign in seconds is considered as a measure of work efficiency and is expressed as the number of Vee-Bee seconds. The name Vee-Bee is derived from the initials of V. Bahrmer, the Swedish who created this experiment. The method is suitable for dry concrete; For concrete with a slope of more than 50 mm, the remoulding is very quick and the time cannot be measured.

 

Apparatus

Vee-Bee consistometer (IS: 1199-1959) shown in Fig. below consists of a vibrating table mounted on elastic supports; Cylindrical container; Sheet metal slump cone; Standard iron tamping rod; Weighing balance and Trowels.

 

Description of Apparatus

The vibrating table of size 380 mm long and 260 mm wide is supported on rubber shock absorbers at a height of about 305 mm above the floor level. An electrically operated vibrator is provided under the table. The assembly is mounted on a base that rests on three rubber supports.

The open sheet metal slump at both ends is placed in a conical moulded cylinder container, which is mounted on a vibrating table with wing nuts. The cone is 300 mm high and its bottom and top diameters are 200 and 100 mm respectively. A swivel arm holder is mounted at the base and is propelled by another rotating arm telescope with a funnel and guide sleeve. The spiral arm can be separated from the vibrating table. A graduated rod, with a transparent disc screwed into one end of it, is fixed by a spiral arm through the guide sleeve. The sized sections on the wire record the collapse of the concrete cone in the cylinder container.

The standard iron tamping rod is 20 mm in diameter and 500 mm in length.

 

Procedure

Step 1: Place the sheet metal slump cone within the cylindrical container of the consistometer. Fill the cone in four layers, each approximately one-quarter of the height of the cone. Tamp each layer with twenty-five strokes of the rounded end of the tamping rod. The strokes are distributed in a uniform manner over the cross-section of the cone and for the second and subsequent layers, the tamping bar should penetrate into the underlying layer. After the top layer has been rodded, struck off level the concrete with a trowel so that the cone is exactly filled.

 

Consistometer (IS: 1199-1959)

Step 2: Move the glass disc attached to the swivel arm and place it just on the top of the slump cone in the cylindrical container. Adjust the glass disc so as to touch the top of the concrete cone and note the initial reading on the graduated rod.

 

Step 3: Remove the cone mould from the concrete immediately by raising it slowly and carefully in the vertical direction. Lower the transparent disc on the top of the concrete. Note down the reading on the graduated rod.

 

Step 4: Determine the slump by taking the difference between the readings on the graduated rod recorded in Steps 2 and 3 above.

Step 5: Switch on the electrical vibrations and simultaneously start the stopwatch. Allow the concrete to be remoulded by spreading out in the cylindrical container. The vibrations arc continued until the concrete is completely remoulded, i.e., the surface becomes horizontal and the whole concrete surface adheres uniformly to the transparent disc.

 

Step 6: Record the time required for complete remoulding in seconds which measures the workability expressed as a number of Vee-Bee seconds.

 

Observations and Calculations

Initial reading on the graduated rod,	'a' mm
Final reading on the graduated rod,	b' mm
slump	(b) – (a)mm
Time for complete remoulding	seconds

 

The consistency of the concrete is ______ Vee-Bee seconds

 

Precautions

1. The inner surface of the axis should be thoroughly cleaned and freed from moisture.

2. The stroke of the tamping wire should be applied uniformly through the entire depth of the concrete of the previous layer.

3. Lift the sloping cone upwards and gently remove it so as not to disturb the concrete cone.

4. Should be tested from any vibration source.

5. Once the transparent disc rider has completely covered the concrete and all the holes in the surface of the concrete have disappeared, the redesign of the concrete should be considered complete.

 

 

Discussion

Compared to the collapse test and the compression factor test, the Vee-bee test has the advantage of receiving the same treatment as the concrete in the test actually in practice. As the remoulding finish is visibly detected, the difficulty in establishing the endpoint of the test introduces the source of the error, which is more pronounced for high-performance concrete mixes and consequently records lower Vee-bee time. For concrete with a slope of more than 125 mm, the redesign can be very quick and time-consuming. Therefore, the test is not suitable for high-performance concrete, i.e., for slopes of 75 mm or more. To alleviate this problem to some extent, an automated device that records the movement of the disk against time may be fitted. The Vee-bee test is suitable for low and very low-performance hard concrete mixtures.

Out of the three methods recommended by IS:1199-1959 namely, slump test; compaction factor test; and Vee-Bee consistency test, the slump test is perhaps the most widely used primarily because of its simplicity. But the test is suitable only for concretes of medium to high workability (i.e., slump 25 to 125 mm). For very stiff mixes having zero slumps, the slump test does not indicate any difference in the concretes of different workability. It should be appreciated that the different concretes having the same slump may indeed have different workability under the site conditions. On the other hand, the compaction factor test has been held to be more accurate than the slump test, especially for concrete mixes of medium and low workability (i.e., compacting factor of 0.9 to 0.8). For concrete of very low workability (i.e., compacting factor of 0.70 and below, which cannot be fully compacted in the manner described in the test) this test is not suitable. In addition, the tendency of some dry mixes to stick in the hoppers introduces a source of error.

 

Consistency measurements by various test methods (as per ACI Committee 211)

Workability description	Workability measurement		Vee-Bee time seconds
	Slump, mm	Compacting factor
Extremely dry	-	-	32-18
Very stiff	-	0.70	18–10
Stiff	0–25	0.75	10–5
Stiff plastic	25–50	0.85	5–3
Plastic	75–100	0.90	3–0
Flowing	150–175	0.95	-

 

 

There is no rigid correlation between the workability of concrete as measured by different methods. The table below gives the range of expected values obtained by different test methods for comparable concretes. In the absence of definite correlations between the different measures of workability under different conditions, it is recommended that for a given concrete, appropriate test method be decided beforehand and the workability expressed in such test only rather than interpreting from the results of other tests.

 

Reference:

IS 1199-1959 (reaffirmed 2008): Methods of Sampling and Analysis of Concrete

IS 6461 (Part 10) -1973 (reaffirmed 2011): Glossary of Terms Relating to Cement Concrete; Part 10:

BS EN 12350-3:2000, Testing of Fresh Concrete: Ve-Bee Test

Gambhir, M. L., Concrete Technology, 4th edition, McGraw-Hill Education (India), 2009

6. Gambhir, M. L. and Neha Jamwal, Building Materials: Products, Properties and Systems, McGraw-Hill Education (India), 2011.

 

FAQ’S ON VEE-BEE TEST

What is the Vee Bee consistency test?

The test measures the comparative effort required by vibration to transfer the concrete mass from one definite shape to another (i.e., from a conical shape to a cylindrical shape). The amount of effort required to complete the transition (called remoulding effort) is taken in seconds

 

What Is Relevant Is Code Of Vee-Bee Test?

IS: 1199 – 1959

 

Why do we do the Vee Bee test?

The main purpose of the Vee-Bee test is to determine the workability of freshly mixed concrete. The Vee-Bee test provides an indication of the movement and compatibility of freshly mixed concrete.

NATIONAL STANDARDS

1. IS 1199-1959 (reaffirmed 2008): Methods of Sampling and Analysis of Concrete

2. IS 6461 (Part 10) -1973 (reaffirmed 2011): Glossary of Terms Relating to Cement Concrete; Part 10: Tests and Testing Apparatus

REFERENCES

BS EN 12350-3:2000, Testing of Fresh Concrete: Vee-Bee Test

Gambhir, M. L., Concrete Technology, 4th edition, McGraw-Hill Education (India), 2009

Gambhir, M. L. and Neha Jamwal, Building Materials: Products, Properties and Systems, McGraw-Hill Education (India), 2011.