HOW TO PERFORM VEE-BEE CONSISTANCY TEST FOR FRESH CONCRETE ?

VEE-BEE CONSISTANCY TEST FOR FRESH CONCRETE

The workability of fresh concrete is a composite property, which includes the diverse requirements of stability, mobility, compactability, placeability and finishability. There are different methods for measuring the workability. Each of them measures only a particular aspect of it and there is really no unique test, which measures workability of concrete in its totality. This test gives an indication of the mobility and to some extent of the compactibility of freshly mixed concrete. The test measures the relative effort required to change a mass of concrete from one definite shape to another (i.e., from conical to cylindrical) by means of vibration. The amount of effort (called remoulding effort) is taken as the time in seconds, required to complete the change. The results of this test are of value when studying the mobility of the masses of concrete made with varying amounts of water, cement and with various types of grading of aggregate. The time required for complete remoulding in seconds is considered as a measure of workability and is expressed as the number of Vee-Bee seconds. The method is suitable for dry concrete. For concrete of slump in excess of 50 mm, the remoulding is so quick that the time cannot measured.

OBJECTIVE

To determine the consistancy of stiff concrete.

APPARATUS

• Cylindrical mould,

• Vee-Bee apparatus (consisting of vibrating table, slump cone)

• Standard Temping rod,

• Stop watch and

• Trowels    

PROCESURE

• The slum mould is filled with concrete in three layers, each being rammed as in slum test.

• The glass plate rider is brought to level so as to just touch the top of the cone when swung. vertical scale reading at this level is noted.

• Now the coneis lifted up and slump of concrete is found noting the reading in thevertical scale as the glass plate rider is brought in level with the top of the slumped concrete.

• Now the vibrating table is set to motion and the vibration is continued until the whole concrete reads out in the cylindrical container. the interval of time taken for the concrete to spread out fully is noted. this interval of time is called vee-bee test value and is regarded as a measure of workability of concrete. 

CALCULATION AND OBSERVATION 

Initial reading on the graduated rod (a)

Final reading on the graduated rod, (b) 

Slump = (b) – (a), in cm time for complete remoulding, seconds.

RESULT

The consistency of the concrete is reported in seconds.

VEE-BEE STANDARD VALUES

Workability Description	Vee-Bee Time (in Second)
Extremely Dry	32-18
Very Stiff	18-10
Stiff	10-5
Stiff Plastic	5-3
Plastic	3-0
Flowing	—