Compaction factor test
This test is more precise and Sensitive than the slump test the and was developed in UK.
The test office a direct and reasonably reliable assessment of workability of concrete since it measures the degree of compaction imparted to concrete for a standard amount of work.
It is particularly useful for concrete mixesof medium and low workabilities as are normally used when concrete is to be compacted by vibration; such dry concretes are insensitive to slump test.
For concrete of very low workability of the order of 0.7 for below and for very high workability of 0.98 or above.
The test is not suitable, because this concrete cannot be fully compacted for comparison in the manner described in the test. A diagram of the apparatus used in compacting factor test is
shown in figure.
The hopper is filled level with its brim and the trap-door is opened to allow the concrete to fall into the flower hopper.
Certain mixes have tendency to stick is one or both of the hoppers.If this occurs, the concrete may be helped through by pushing the rod gently into the concrete from the top.
During this process, the cylinder should be covered by the trowels. Immediately after the concrete has come to rest, the cylinder is uncovered, the trap-door of the lower hopper is opened, and the concrete is allowed to fall into the cylinder.
The excess of concrete remaining above the level of the top of the cylinder is then cutoff-.
The weight of the concrete in the cylinder is then determined to the nearest 10g as the weight or partially compacted concrete.
The cylinder is refilled with concrete from the same sample is layers of approximately 50 mm, the layers being heavily rammed or preferably vibrated so as to obtain full compaction.
The top surface of the fully compacted concrete is carefully struck off level with the top of the cylinder.
Compacting factors is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete.
It is normally stated to the nearest second decimal place.
Note: The test is sufficiently sensitive to enable differences in
workability arising from the initial process in the hydration of the
cement. Each test, therefore, is carried out at a constant time interval after the mixing is completed if strictly comparable results are to be obtained,
A convenient time for releasing the concrete from the upper hopper has been found to be 2 minutes after the completion of mixing.Some of the basic assumptions of the test are not correct. The work done to overcome surface friction of the measuring cylinder probably varies with the characteristics of the mix.
For concretes with very low workability, the actual work require to obtain full compacting depends on the richness of a mix while the compacting factor remains sensibly unaffected.
Thus it follows that the generally held belief that concretes with same compacting factor require the same amount of work for full compaction cannot always be justified.
Further, the procedure for placing concrete in the messaging cylinder bears no resemblance to methods commonly employed in the field.
This test is more precise and Sensitive than the slump test the and was developed in UK.
The test office a direct and reasonably reliable assessment of workability of concrete since it measures the degree of compaction imparted to concrete for a standard amount of work.
It is particularly useful for concrete mixesof medium and low workabilities as are normally used when concrete is to be compacted by vibration; such dry concretes are insensitive to slump test.
For concrete of very low workability of the order of 0.7 for below and for very high workability of 0.98 or above.
The test is not suitable, because this concrete cannot be fully compacted for comparison in the manner described in the test. A diagram of the apparatus used in compacting factor test is
shown in figure.
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procedure for compaction factor test
The sample of concrete to be tested is placed gently in the upper hopper.The hopper is filled level with its brim and the trap-door is opened to allow the concrete to fall into the flower hopper.
Certain mixes have tendency to stick is one or both of the hoppers.If this occurs, the concrete may be helped through by pushing the rod gently into the concrete from the top.
During this process, the cylinder should be covered by the trowels. Immediately after the concrete has come to rest, the cylinder is uncovered, the trap-door of the lower hopper is opened, and the concrete is allowed to fall into the cylinder.
The excess of concrete remaining above the level of the top of the cylinder is then cutoff-.
The weight of the concrete in the cylinder is then determined to the nearest 10g as the weight or partially compacted concrete.
The cylinder is refilled with concrete from the same sample is layers of approximately 50 mm, the layers being heavily rammed or preferably vibrated so as to obtain full compaction.
The top surface of the fully compacted concrete is carefully struck off level with the top of the cylinder.
Compacting factors is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete.
It is normally stated to the nearest second decimal place.
Note: The test is sufficiently sensitive to enable differences in
workability arising from the initial process in the hydration of the
cement. Each test, therefore, is carried out at a constant time interval after the mixing is completed if strictly comparable results are to be obtained,
A convenient time for releasing the concrete from the upper hopper has been found to be 2 minutes after the completion of mixing.Some of the basic assumptions of the test are not correct. The work done to overcome surface friction of the measuring cylinder probably varies with the characteristics of the mix.
For concretes with very low workability, the actual work require to obtain full compacting depends on the richness of a mix while the compacting factor remains sensibly unaffected.
Thus it follows that the generally held belief that concretes with same compacting factor require the same amount of work for full compaction cannot always be justified.
Further, the procedure for placing concrete in the messaging cylinder bears no resemblance to methods commonly employed in the field.
Questions which are covered in this article related to compacting factor test
What is compaction factor?
The compaction factor is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete, for better understanding please read full article.
How do you calculate compaction factor?
To Calculate compaction factor you have to calculate ratio of the weight of partially compacted concrete to the weight of fully compacted concrete, for better understanding please read full article.
How many hoppers consists the compaction factor test apparatus?
You Can Easily See Above;Compacting factor apparatus consists of two conical hoppers mounted above a cylindrical mould and fixed to a stand one above the another. The hoppers are provided with trap doors at the bottom
Why compaction factor test is done?
Compaction factor test is Done To Know The workability for concrete which is conducted in laboratory.
Compaction factor test in Civil engineering?
please read full ARTICLE
What is compaction factor test?
it is used to know the workability of concrete
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