Expt No:

Date:

VEE-BEE TEST

AIM:

To determine the workability of concrete using Vee-Bee apparatus.

DEFINITION:

This is a good laboratory test to measure indirectly the workability of

concrete.

The test consists of a vibrating table, a metal pot & a standard iron rod.

APPARATUS:

The apparatus consists of vibrating table, metal pot, a sheet metal cone and

standard iron rod.

PRINCIPLE:

The test is based on the principle of measuring the energy required o fill &

compact fresh concrete in a mould. The amount of effort required to change the

shape of

a sample of concrete from one form to another gives the workability of concrete.

The tie

necessary for the remoulding of concrete, when placed over a vibrating table &

vibrated

is a measure of the input energy required for compaction. This is expressed in Vee-

Bee

seconds. Hence workability is expressed as the time necessary for the remoulding

to be complete (i.e., in Vee-Bee seconds).

During the remoulding, some compaction takes place & the volume of

concrete gets reduced. Taking into consideration the decrease of volume due to the

compaction, the Vee-Bee second is multiplied by the ratio of volume of concrete

after & before the vibrations.

TEST SETUP:

In the Vee-Bee test, the time taken to transform the concrete from conical

shape to cylindrical shape is measured. A standard slump cone is placed in a

OBSERVATIONS AND CALCULATIONS:

Mix ratio =

Height of slump cone, h =

Top radius of slump cone,r1 =

Bottom radius of slump cone,r2 =

Height of vibration cylinder, H =

Radius of vibration cylinder, r =

Volume of concrete before vibration, V1 = (πh(r23-r1

3))/(3(r2-r1)

W/C

ratioSlump

Vee-Bee

Seconds

(s)

Height of

cone after

vibration, h2

(cm)

Volume of cone

after vibration,

V2= πr2 h2

(cm3)

Volume ratio

(V2/V1)

Corrected

Vee-Bee

seconds

(s)

cylinder of standard size, the cylinder being mounted rigidly on a vibrating table.

Freshly prepared concrete is placed inside the slump cone in four layers & is

compacted by tamping 25 times using a standard tamping rod. A sliding glass disc

gives the height of concrete at different levels. After removing the slump cone, the

substance of concrete can be noted using the glass plate rider. This gives the

slump value of concrete.

Vibration is given to the table till the remoulding is complete i.e., when the

glass plate rider is completely covered with concrete & all cavities in the surface of

concrete have disappeared. Stopwatch operated at the start of vibration gives the

Vee-Bee seconds. The time required for the remoulding to be complete is noted as

the workability of the mix. For different water / cement ratios, the test is repeated.

A graph drawn between slump & Vee-Bee seconds can be used to study the

behaviour of concrete.

PROCEDURE:

1. Clean the slump cone & cylinder well.

2. Prepare the concrete of a nominal mix with an initial water / cement ratio =

0.5.

3. Place the slump cone inside the cylinder & fill it as described earlier in

layers.

4. Remove the slump cone & note the subsidence of concrete with the help of

glass plate rider.

5. Vibrate the table till the concrete is completely remoulded. When the

vibration is started, start the stopwatch.

6. Note the time taken for the complete transformation from conical shape to

cylindrical form.

7. Repeat the test using different water / cement ratio such as 0.6, 0.7, 0.8 etc.

8. Draw a graph taking Vee-Bee seconds along X-axis & slump along Y-axis.

RESULT:

Workability of concrete as expressed in terms of Vee-Bee seconds for 1:2:4

mix ratio

at water / cement ratio 0.6 = s

at water / cement ratio 0.7 = s

at water / cement ratio 0.8 = s

Workability of concrete as expressed in terms of Vee-Bee seconds for

1:2:4mix ratio at water-cement ratio, 0.6 = s.