Workability of concrete is the essential property of fresh concrete. Workability of concrete means the ease of working with concrete.
Concreting includes following process:
It is necessary to measure workability of concrete before and during the concreting work because many factors affect the workability of fresh concrete like, weather conditions, type of work, types of ingredients which are used to make concrete etc. According to such factors, the requirement of workability like low workability, medium workability, high workability differs for each set of conditions.
Various methods are used to measure the workability of concrete. Following are the main test carried out in laboratory to check the workability.
Here we are discussing the vee bee test of concrete, its testing apparatus, procedure, result etc.
Vee bee test is the pure laboratory test to measure workability of fresh concrete. Vee bee test is also called ‘Vee Bee Consistometer Test’, ‘Vebe Test’ etc. The name ‘vee bee or vebe’ is derived from the initials of V. Bahrner from Sweden, who developed this test. In the vee bee test, workability is measured with the aspect of mobility and compactibility.
As you know, the workability of fresh concrete is defined as the amount of useful internal work necessary to produce 100% compaction. Vee bee test gives the time required to achieve compaction, which is related to the total work done; hence vebe test is a good test to measure the workability of concrete indirectly.
In the vee bee consistometer test, the shape of concrete is changed from the slump cone shape to the cylindrical shape through the vibration process; this is called remoulding effect. This remoulding effect is measured in seconds which is called vee bee degree or vee bee seconds.
Vee bee consistometer test is suitable for very dry concrete whose slump value can’t be measured by slump test, but the vibration is too strong for the concrete where slump is greater than 50 mm, hence the remoulding activity can’t be measured or it is difficult to measure in seconds.
There are various standard guidelines available to perform the vebe test. Such as,
Here, we have mentioned vee bee consistometer test as per the IS: 1199- 1959.
Vee bee consistometer is consist of the followings components.
Slump Value = Final Reading – Initial Reading: Slump value is the difference between the final reading and initial reading, which are taken from the graduated rod.
Vee Bee Degree: In the vee bee consistometer test, the shape of concrete is changed from the slump cone shape to the cylindrical shape in seconds, the required time to change the shape of concrete is known as vee bee degree.
Recommended results of vee bee test of concrete are as follows:
Vee bee test of concrete is more suitable for dry concrete than the other types of workability test such as slump test, flow test etc. and that is why it is mostly used for dry concrete or concrete with a low water-cement ratio.