Compaction Factor Test
The compaction factor is defined as the ratio of the mass of compacted concrete in the compaction factor apparatus to the mass of fully compacted concrete.
The compaction factor test is carried out to measure the degree of workability of fresh concrete with regard to the internal energy required for compacting concrete thoroughly.
The compacting factor test is used to find out the low workability of concrete. it is a fact that the slump cone test of concrete is not given accurate results for the low workability of concrete when the slump is <50mm.
This test is more precise than the slump test but it is less common. The size of the apparatus makes it difficult to conduct the test in the field.
The compaction factor test was developed by Road Research Laboratory in the United Kingdom.
Read More: Slump Test – Type Of Slump & Test Method
Test of Concrete
The following are different concrete tests,
- Rebound Hammer Test
- Tensile Strength Test of Concrete
- Ultrasonic Pulse Velocity Test on Concrete
- Concrete Cube Test
Compaction Factor Apparatus
As per IS1199:1999 Compaction factor test apparatus consists of,
- Two conical hoppers and a bottom cylinder which is arranged as shown in below fig.
- A steel rod of 1.6 cm diameter with a length of 61cm is used to tamp the concrete
- Weight balance is used to weigh the concrete.
Compaction Factor Test Procedure
- The sample of concrete to be tested shall be placed gently in the upper hopper, using the hand scoop.
- The hopper shall be filled level with its brim and the trap door shall be opened so that the concrete falls into the lower hopper.
- Certain mixes have a tendency to stick in one or both of the hoppers. If this occurs, the concrete may be helped by pushing the rod gently into the concrete from the top.
- Immediately after the concrete has come to rest, the cylinder shall be uncovered, the trap door of the lower hopper opened, and the concrete allowed to fall into the cylinder.
- The excess concrete remaining above the level of the top of the cylinder shall then be cut off by holding a trowel.
- Weight the cylinder with concrete to the nearest 10 g. This weight is known as the weight of partially compacted concrete (W1).
- Empty the cylinder and then refill it with the same concrete mix in layers approximately 5 cm deep, each layer being heavily rammed to obtain full compaction.
- Level the top surface.
- Weigh the cylinder fully compacted. This weight is known as the weight of fully compacted concrete (W2).
- Find the weight of the empty cylinder (W).
Read More: Tensile Strength Of Concrete – Test & Result
Observation Table
| Sr. No. | Description | Sample 1 | Sample 2 | Sample 3 |
| 1 | Weight of Empty Cylinder (W1) | |||
| 2 | Wt. of Empty Cylinder + Free Fall Concrete(W2) | |||
| 3 | Wt. of Empty Cylinder + Hand Compacted Concrete (W3) | |||
| 4 | Wt. of partially Compacted Concrete(Wp = W2 – W1) | |||
| 5 | Weight of Fully or Proper Compacted Concrete (Wf = W3 – W1) | |||
| 6 | Compaction Factor = Wp/Wf |
Calculation of Compaction Factor Value
Compaction factor = Weight of Partially Compacted Concrete(Wp) / Weight of Fully Compacted Concrete(Wf)
Result
1. Compaction Factor of Concrete is found to be =
2. The vertical difference between the top of the mould and the displaced original center of the top surface of specimen…………mm.
| Workability | Compaction Factor |
| Very Low | 0.78 |
| Low | 0.85 |
| Medium | 0.92 |
| High | 0.95 |
Why Compaction Factor Test More Important than the Slump Test for the Workability of Concrete
Generally, the Slump Test is used to determine workability on the field, But it is not effective when the value of the slump is lower than 50mm.
Low-workability concrete is used in the mass concreting of foundations and light-reinforced structures. In such a situation the compaction factor test is more suitable.
Moreover, the compaction test gives more accurate results as compared to the slump test.
Relation Between Slump Test Result and Compaction Factor Test Result
| Workability | Slump in mm | Compaction Factor |
| Very Stiff | – | 0.70 |
| Stiff | 0 to 25 | 0.75 |
| Stiff Plastic | 25 to 50 | 0.85 |
| Plastic | 75 to 100 | 0.90 |
| Flowing | 150 to 175 | 0.95 |
FAQs
What is the compaction factor test?
The compaction factor test is carried out to measure the degree of workability of fresh concrete with regard to the internal energy required for compacting concrete thoroughly. The compaction factor is defined as the ratio of the mass of compacted concrete in the compaction factor apparatus to the mass of fully compacted concrete.
Why compaction factor test is done?
The compaction factor test is carried out to measure the degree of workability of fresh concrete with regard to the internal energy required for compacting concrete thoroughly. The compacting factor test is used to find out the low workability of concrete.
You May Also Like
