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 50mm, the remoulding is so quick that the time cannot measured.
Fig. 1: Vee-Bee Consistometer
a) A vibrator table resting upon elastic supports
b) A metal pot
c) A sheet metal cone, open at both ends
d) A standard iron rod, Tamper (20 mm in diameter and 500 mm length)
Fig. 2: Balance
Balance should be able to weigh upto 1 g accuracy.
IS 1199:1959 Methods of Sampling and Analysis of Concrete (Eleventh revision). Reaffirmed- Dec 2013.
|Work Description||Workability Measurement||Vee-Bee time (seconds)|
|Slump (mm)||Compaction Factor|
|Moist earth||-||-||40 to 25-20|
|Very Dry||-||0.70||20 to 15-10|
|Dry||0 - 25||0.75||10 to 7-5|
|Plastic||25 - 50||0.85||5 to 4-3|
|Semi Fluid||75 - 100||0.90||3 to 2-1|
|Fluid||150 - 175||0.95||More Fluid than 1|
Table 1 : Workability of Concrete based on Vee-Bee Test