The compaction factor test is used for concrete which have low workability for which slump test is not suitable.
The compacting factor test is performed to ascertain the workability of the concrete. The slump test does not give accurate results for low worability of concrete when slump is<50mm.
The compaction factor test is a workability test for concrete conducted in the laboratory. It was developed by the Road Research Laboratory in the United Kingdom and is used to determine the workability of concrete.

The compaction factor is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete.

Compaction factor test Apparatus:-

Compaction factor test apparatus consists of two conical hoppers and a bottom cylinder which is arranged properly
Steel rod of 1.6cm, diameter with a length of 61cm is is used to level the concrete.
A weight balance is used to weight the concrete.
Hand scoop (15.2 cm long) and a balance.

Compaction factor apparatus


1.Prepare M15 grade concrete.the mixture with 1: 2: 4 by mixing the required amount of water according to the water cement ratio and mix the fresh concrete. 

2.See that the inner surface of the conical hopper should be free of moisture and apply grease to it. Close the trap door of the upper/top hopper. 

3.Then measure the weight of the empty bottom cylinder as W1.

4.Fill fresh concrete into the upper/top conical hopper without disturbing the sample.

5.After this, the trap door of an upper hopper is opened. Thus the concrete falls on the lower/bottom hopper.

6.Wait for 2-3 seconds and check if the entire concrete has fallen from the top hopper to the bottom hopper. If not, a slight tamping is done until the entire concrete falls into the bottom hopper.

7.Now open the bottom hopper trap door, and the entire concrete has fallen on the cylinder. Using the trowel, remove excess concrete on the top surface of the cylinder.

8.Weigh the cylinder with partially filled concrete as W2.

9.Then the cylinder is emptied, and the concrete sample is filled again in 3 layers, each layer being given 25 blows using a steel rod. Now, the concrete inside the cylinder is completely compacted.

10.Measure the weight of the cylinder completely with concrete as W3 .

Dimensions of compacting factor test apparatus


• Compression factor test gives more information than slump test.

• The test is a dynamic test and is thus more suitable for concrete mixture static tests.


• The large and heavy nature of the device reduces its usefulness in the field. In addition, the test method requires an equilibrium to measure the mass of concrete in the cylinder.

• The amount of work applied to the concrete being tested is a function of friction between the concrete and the hopper, which probably does not reflect additional conditions.

• The test method does not use vibration, the main compaction method used in the field.

• This test is commercially available and is often used.

Calculation of Compaction Factor Value:
The compaction factor is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete.
Compacting Factor = (weight of partially compacted concrete) / (weight of fully Concrete Concrete)
                                  = W2 – W1 / W3 - W1
W= Weight of empty cylinder.
W=  Weight of partially compacted concrete.
W=  weight of fully Concrete Concrete.
Result of Compaction Factor
Compaction factor of the concrete =
The Compaction factor values ranges from 0.7 to 0.95.

Compacting factor with respect to workability

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