Testing of Fresh Concrete: Vebe Test
Introduction
The Vebe test use to measure concrete’s workability by determining the characteristics of
mobility and compatibility. The test's basic idea is to mold the concrete into a different form
while measuring how long it takes. The motive of the test in this experiment is to determine
the workability and consistency of the in-situ concrete after varying its water content to
identity its effect on the fresh properties.
Aims
To determine the effect of water content on the consistency of the concrete measured
by the Vebe test as per BS EN 12350-3:2009 Testing fresh concrete – Part 3: Vebe
test.
Objectives
To study how the Vebe time varies with the different water content added to the
concrete mix.
Literature Review
The name is derived from the initials of VB ~ Horner, Sweden, who developed the test. The test is BS
1881-104: 1983, BS EN 12530 3: 2000 and ACI 211.3R 02.
The test involves vibrating a sample of concrete to remold it; the quantity of time it takes for
the material to remold is measured as the Vebe time. It is assumed that the energy input
required for complete compression is a measure of the feasibility of the mixture and is expressed in
Vebe seconds that is the time required for operation.
Vebe test also known as Humboldt’s Vebe Consistometer method is based on the same
principle of the simple slump cone test, but it has the advantage of a mechanized action. After
removing the slump cone, the concrete undergoes a vibration to determine slump. The Vebe
test is a good laboratory technique to measure indirectly the workability of concrete since the
time measured to transfer the shape of the concrete mix from a frustrum cone to a cylinder by
vibrating and compacting the mix is measured.
The slump cone is placed inside a cylindrical-shaped container that is fixed firmly to the
Vebe table. The slump cone is filled in a standard way and this cone is removed. On the end
of the concrete is put the clear plastic disk.The clear plastic disk will be considered fully
remolded once it has been completely covered in concrete and all of the original surface
cavities have disappeared.
Methodology
List of apparatus and their description
S.N APPARATUS PICTURE DESCRIPTION
1. Vebe Consistometer Frustrum of cone of:
Height:300mm
Base diameter:200mm
Top Diameter: 10mm
The cone keeps the
concrete in place.
The scale is used to
measure the slump
height.
2. Tamping Rod Diameter:16 cm
Length:60cm
It should have rounded ends.
It is used to compact
the concrete.
3. Scoop
It is used to pour the concrete
into the cone to fill it in layers
before compaction.
4. Hand Trowel It is used to mix and remix the
concrete before filling the cone
and to level off the upper
surface of the cone so as to
strike off
the excess concrete.
5. Digital Stopwatch
It is used as a time measuring
device.
Procedures:
1.The proportioned aggregates, cement and water are mixed using trowels to obtain a
homogeneous mixture on a mixing tray.
2. The cone is fitted inside a cylindrical container fixed to a flat horizontal base.
3. A funnel is placed at the top to facilitate the pouring of concrete.
4. Concrete is scooped and poured into the cone in three layers with each layer being
approximately one-third of the cone post-compaction.
5. The tamping rod is used to compact each layer with 25 strokes.
6. The cone is ultimately fully filled, and the funnel is removed.
7. The top surface of the concrete is levelled and finished off using the hand trowel to strike
off the excess concrete.
8. The cone is raised slowly in a vertical manner to allow the concrete to slump.
9. The type of slump obtained is verified if it is a true slump to resume the test.
10. The vibrating table is turned on and the stopwatch is started at the same time. When the
disc is completely in contact with the cement grout, the timer is stopped and the vibrating
table is switched off. The time obtained is the Vebe time.
Precautions during experiment:
Ensure that the internal surface of the cone is damp (not too wet) and clean before
starting test so that the slump can settle into the metallic cylinder without sticking to
the cone.
The mold should be held firmly against the base using the foot pieces.
Mold should be raised in 2-5 s by swiftly raising it without making lateral or twisting
motion which may affect the shape of the concrete inside.
The test should be carried out at a place away from any source of vibration than the
apparatus itself.
Safety precautions:
Direct contact with alkaline cement should be avoided, especially when it is mixed
with water to form an alkaline product.
Washing or rinsing the affected areas with water is highly recommended open direct
contact with cement.
Gloves and safety google should be worn when handling equipment.
Lab coat with long sleeves should be worn to minimize contact to the skin during
mixing or handling cement.
Results and Analysis
The data collected from the test has been summarized in the table below:
Mix Water to cement Slump height/mm Vebe time/s
ratio
1 0.72 110 2.10
2 0.78 Invalid Invalid
3 0.66 30 4.15
4 0.74 115 1.42
Analysis of Data
A graph of Vebe time/s against water to cement ratio is drawn below:
Effect of water content on vebe time
4.5
4
3.5
3
Vebe time/s
2.5
2
1.5
1
0.5
0
0.64 0.66 0.68 0.7 0.72 0.74 0.76 0.78 0.8
Water to cement ratio
Vebe time/s Polynomial (Vebe time/s)
Discussion and Conclusion
From the graph plotted, it can be deduced that as water to cement ratio increases from 55% to
63%, the Vebe time decreases from 4.00 s to 1.42 s. When water is reduced, the Vebe time
increases as workability increases.
However, for the concrete mix 2 which had a water to cement ratio of 66%,we were unable
to calculate the vebe time as upon removal of the cone(slump test), the concrete grout
collapsed.This is an indication that the water-cement ratio is too high or concrete mix is too
wet or it is a high workability mix, for which a slump test and vebe tests are not appropriate
We can thus conclude that our experiment is a success as it clearly demonstrates the effect of
the water to cement ration upon the vebe time. However the Vebe test is only indicative of
the workability of fresh concrete but not a universal decisive method.
