The vee-bee test is another method for determining the workability of concrete. The name vee-bee is taken from the initials of V. Bahrner, the inventor of this test from Sweden. This test works well with stiff concrete mixes that have a low or extremely poor workability.
The needed measure of workability in this test is the time required for complete remoulding in seconds, which is given as the number of vee-bee seconds.
Apparatus Used in Vee-Bee Test
The vee-bee test equipment consists of a vibrator table supported by elastic supports, a metal pot, a cylindrical pan, a slump cone, and a glass or plastic disc attached to a free-moving iron rod that serves as a reference endpoint.
You can have a look at the above image to understand the various units of the apparatus.
Procedure
- In the cylindrical pot of the consistometer, a slump test is done.
- The glass disc attached to the swivel arm is moved to just above the top of the slump cone in the pot, and the position of the concrete cone is measured by adjusting the glass disc attached to the swivel arm before the cone is hauled up.
- By lowering the glass disc on top of the concrete cone and lifting it up, the slump is registered on the graded rod.
- The electrical vibrator is turned on, and the concrete in the pot is allowed to expand out.
- The vibration is sustained until the entire concrete surface adheres equally to the glass disc, and the time it takes to do this is recorded using a stop watch.
- The Vew-Bee degree, which is equal to the recorded duration in seconds, is used to represent the concrete’s consistency.
You can have a look at the values of vee-bee degree for different placing conditions in the table below.
Observation
Vee Bee Degree is the amount of time it takes for the shape of concrete to change from slump cone to cylindrical in seconds.
| Degree of Workability | Vee-Bee degree/ Vee-Bee Time in seconds |
| Very Low | 20 – 10 |
| Low | 10 – 5 |
| Medium | 5 – 2 |
| High | 2 – 0 |
Vee-Bee is an excellent laboratory test, especially for extremely dry mixtures. This is in contrast to the compacting factor test, where the tendency of some dry mixes to stick in the hoppers can introduce inaccuracy.
The vee-bee test also has the benefit that the concrete treatment during the test is remarkably similar to the way of placement in practice. The Vebe test can quickly detect the cohesiveness of concrete by observing the dispersion of the coarse aggregate following the vibrations.