Testing Fresh Concrete. Slump Test

Slump test
The slump test is a means of assessing the consistency of fresh concrete. It is

used, indirectly, as a means of checking that the correct amount of water has
been added to the mix. The test is carried out in accordance with BS EN
12350-2, Testing fresh concrete. Slump test.
The steel slump cone is placed on a solid, impermeable, level base and filled
with the fresh concrete in three equal layers. Each layer is rodded 25 times to
ensure compaction. The third layer is finished off level with the top of the
cone. The cone is carefully lifted up, leaving a heap of concrete that settles or
‘slumps’ slightly. The upturned slump cone is placed on the base to act as a
reference, and the difference in level between its top and the top of the
concrete is measured and recorded to the nearest 10mm to give the slump of
the concrete.
When the cone is removed, the slump may take one of three forms. In a true
slump the concrete simply subsides, keeping more or less to shape. In
a shear slump the top portion of the concrete shears off and slips sideways.
In a collapse slump the concrete collapses completely. Only a true slump is
of any use in the test. If a shear or collapse slump is achieved, a fresh sample
should be taken and the test repeated. A collapse slump will generally mean
that the mix is too wet or that it is a high workability mix, for which the flow test
(see separate entry) is more appropriate.
Concrete slump test or slump cone test is to determine the workability or consistency of
concrete mix prepared at the laboratory or the construction site during the progress of the
work. Concrete slump test is carried out from batch to batch to check the uniform quality
of concrete during construction.
The slump test is the most simple workability test for concrete, involves low cost and
provides immediate results. Due to this fact, it has been widely used for workability tests
since 1922. The slump is carried out as per procedures mentioned in ASTM C143 in the
United States, IS: 1199 – 1959 in India and EN 12350-2 in Europe.
Generally concrete slump value is used to find the workability, which indicates water-
cement ratio, but there are various factors including properties of materials, mixing
methods, dosage, admixtures etc. also affect the concrete slump value.
Factors which influence the concrete slump
test:
1. Material properties like chemistry, fineness, particle size distribution, moisture
content and temperature of cementitious materials. Size, texture, combined grading, cleanliness
and moisture content of the aggregates,
2. Chemical admixtures dosage, type, combination, interaction, sequence of addition and its
effectiveness,
3. Air content of concrete,
4. Concrete batching, mixing and transporting methods and equipment,
5. Temperature of the concrete,
6. Sampling of concrete, slump-testing technique and the condition of test equipment,
7. The amount of free water in the concrete, and
8. Time since mixing of concrete at the time of testing.
Equipments Required for Concrete Slump

Test
Mold for slump test i.e. slump cone, non porous base plate, measuring scale, temping rod.
The mold for the test is in the form of the frustum of a cone having height 30 cm, bottom
diameter 20 cm and top diameter 10 cm. The tamping rod is of steel 16 mm diameter and
60cm long and rounded at one end.
Sampling of Materials for Slump Test

A concrete mix (M15 or other) by weight with suitable water/ cement ratio is prepaid in
the laboratory similar to that explained in 5.9 and required for casting 6 cubes after
conducting Slump test.
Figure-1: Measuring Slump of Concrete

Procedure for Concrete Slump Cone Test
1. Clean the internal surface of the mould and apply oil.
2. Place the mould on a smooth horizontal non- porous base plate.
3. Fill the mould with the prepared concrete mix in 4 approximately equal layers.
4. Tamp each layer with 25 strokes of the rounded end of the tamping rod in a uniform manner over
the cross section of the mould. For the subsequent layers, the tamping should penetrate into the
underlying layer.
5. Remove the excess concrete and level the surface with a trowel.
6. Clean away the mortar or water leaked out between the mould and the base plate.
7. Raise the mould from the concrete immediately and slowly in vertical direction.
8. Measure the slump as the difference between the height of the mould and that of height point of
the specimen being tested.
Figure-2: Concrete Slump Test Procedure
NOTE:
The above operation should be carried out at a place free from Vibrations or shock and
within a period of 2 minutes after sampling.
Slump Value Observation:

The slump (Vertical settlement) measured shall be recorded in terms of millimeters of
subsidence of the specimen during the test.
Results of Slump Test on Concrete

Slump for the given sample= _____mm
When the slump test is carried out, following are the shape of the concrete slump that can
be observed:
Figure-3: Types of Concrete Slump Test Results

o True Slump – True slump is the only slump that can be measured in the test. The measurement
is taken between the top of the cone and the top of the concrete after the cone has been removed
as shown in figure-1.
o Zero Slump – Zero slump is the indication of very low water-cement ratio, which results in dry
mixes. These type of concrete is generally used for road construction.
o Collapsed Slump – This is an indication that the water-cement ratio is too high, i.e. concrete
mix is too wet or it is a high workability mix, for which a slump test is not appropriate.
o Shear Slump – The shear slump indicates that the result is incomplete, and concrete to be
retested.
Read More:
Various Tests for Workability of Concrete at Construction Site and Recommended
Values
What Is Workability of Concrete? Workability vs. Strength of Concrete
Factors Affecting Workability of Concrete
Concrete Workability – Slump & Compacting Factor Values and Uses
Vee-Bee Test to Determine Concrete Workability using Consistometer

Testing Fresh Concrete. Slump Test

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Slump test

The slump test is a means of assessing the consistency of fresh concrete. It is

3. Air content of concrete,

4. Concrete batching, mixing and transporting methods and equipment,

5. Temperature of the concrete,

6. Sampling of concrete, slump-testing technique and the condition of test equipment,

7. The amount of free water in the concrete, and

8. Time since mixing of concrete at the time of testing.

Equipments Required for Concrete Slump

Sampling of Materials for Slump Test

Figure-1: Measuring Slump of Concrete

2. Place the mould on a smooth horizontal non- porous base plate.

Slump Value Observation:

Results of Slump Test on Concrete

Figure-3: Types of Concrete Slump Test Results

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