Vee-Bee Consistometer Test

This is a good laboratory test to measure indirectly the workability of concrete as per IS: 1199– 1959. The test equipment, which was developed by Swedish Engineer V. Bahrner, is shown in Fig.1. It consists of a vibrating table, a cylindrical pan, a slump cone and a glass or plastic disk attached to a free-moving rod, which serves as a reference endpoint. The cone is placed in the pan. After it is filled with concrete and any excessive concrete is struck off, the cone is removed. Then, the disk is brought into a position on top of the concrete cone and the vibrating table is set in motion and simultaneously a stop watch started. The vibration is continued till such a time as the conical shape of the concrete disappears and the concrete assumes a cylindrical shape. This can be judged by observing the glass disc from the top for disappearance of transparency. Immediately when the concrete fully assumes a cylindrical shape, the stop watch is switched off. The time required for the shape of concrete to change from slump cone shape to cylindrical shape in seconds is known as Vee Bee Degree. This method is very suitable for very dry concrete whose slump value cannot be measured by slump test but the vibration is too vigorous for concrete with a slump greater than about 50 mm.

The Vee bee test is a good laboratory test, particularly for very dry mixes. This is in contrast to the compacting factor test where error may be introduced by the tendency of some dry mixes to stick in the hoppers. The Vee bee test also has the additional advantage that the treatment of concrete during the test is comparatively closely related to the method of placing in practice. Moreover, the cohesiveness of concrete can be easily distinguished by Vee bee test through the observation of distribution of the coarse aggregate after vibration. Table 1 shows the relationship between workability and Vee Bee values.

Fig.1 Vee bee Test Setup

Procedure

1. Mix the dry ingredients of the concrete thoroughly till a uniform colour is obtained and then add the required quantity of water.
2. Pour the concrete into the slump cone with the help of the funnel fitted to the stand.
3. Remove the slump mould and rotate the stand so that transparent disc touches the top of the concrete.
4. Start the vibrator on which cylindrical container is placed.
5. Due to vibrating action, the concrete starts remoulding and occupying the cylindrical container. Continue vibrating the cylinder till concrete surface becomes horizontal.
6. The time required for complete remoulding in seconds is the required measure of the workability and it is expressed as number of Vee-bee seconds.

Table 1 Relationship between Workability and Vee Bee Test Results

Workability Description	Vee-bee Time in Seconds
Extremely dry	32 – 18
Very stiff	18 – 10
Stiff	10 – 5
Stiff plastic	5 – 3
Plastic	3 – 0
Flowing	-