Question

1. Part I : Slump Test

•What is the meaning of tested slump type? Is it an acceptable value? Why?

2. Part II : Compacting Factor Test

•What is the meaning of calculated compacting factor?

3. Are the result from Part I and Part II consistent? Why?

4. In general, what is the difference between slump test and compacting factor test? What is the advantage /disadvantage of each test?

Answer 1

1. Part I : 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.

True slump refers to general drop of the concretemass evenly all around without disintegration. This type of slump is most desirable.

Shear slump indicates that the concrete lacks cohesion. It may undergo segregation and bleeding and thus is undesirable for the durability of concrete.

Collapse slump indicates that concrete mix is too wet and the mix is regarded as harsh and lean.

2.  Part II : Compacting Factor Test

The compacting factor test is performed to find out 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 Value= (W1-W) / (W2-W)

Value of compacton factor	Standard of workability
0.95	Good
0.92	Medium
0.85	Low

3.

Yes, the result of part 1 and part 2 are consitent, Because it is experimently calculated and both are determine for workabilty of fresh concrete only difference is procedure and method. one is for field and another one is for laboratory based.

4. In general, what is the difference between slump test and compacting factor test? What is the advantage /disadvantage of each test?

Main differences between Slump Test and Compacting Factor Test.

The main difference between both is that compaction factor test is more sensitive and precise than slump test and is particularly useful for concrete mixes of low workability and also able to indicate small variations in workability over a wide range.

Advantages of Concrete Slump Test

1. Slump test is very easy and simple. A non-technical person can perform it without any problem.

2. This test does not require any special costly equipment. The sample is not required to be sent to a laboratory. It can be done in the construction area.

3. Slump test does not demand a long-time period to get the result. If we compare with compressive strength test, it requires almost a month to get the result but we can obtain slump value within some minutes.

Limitations/ Disadvantages of Concrete Slump Test

1. For a specimen, more than one shape can be resulted confusing the correct result. If shear slump occurs, it may attain true slump in next test.

2. It cannot differentiate in workability of stiff mixes as it shows zero slumps. In dry range, no difference can be detected between different mixes with different workability.

3. It is not suitable for concrete formed of aggregate higher than 40 mm.

4. It is unreliable for lean mixes. In a lean mix, a true slump may convert into shear or collapse easily. Widely variation can be found from one sample of lean mix and it can be a great confusion to determine the exact result.

Compaction factor test

Advantages:
• The compaction factor test gives more information (that is, about compactability) than the slump test.
• The test is a dynamic test and thus is more appropriate than static tests for highly
thixotropic concrete mixtures.

Disadvantages:
• The large and bulky nature of the device reduces its usefulness in the field. Further, the test method requires a balance to measure the mass of the concrete in the cylinder.
• The amount of work applied to the concrete being tested is a function of the friction between the concrete and the hoppers, which may not reflect field conditions.
• The test method does not use vibration, the main compaction method used in the field.
• Although the test is commercially available, it is used infrequently.