1. objective
The compacting factor test is designed primarily for use in the laboratory but it can also be used in the field.
It is more precise and sensitive than the slump test and is particularly useful for concrete mixes of very low
workability and normally used when concrete is to be compacted by vibration. The method applies to plain and air-entrained
concrete, made with lightweight, normal weight or heavy aggregates having a nominal maximum size of 40 mm or less but not to
aerated concrete or no-fines concrete.
2. apparatus required
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Fig. 1: Balance
Balance should be able to weigh up to 50 Kg with an accuracy to the nearest 10 g.
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Fig. 2: Compaction Factor Apparatus with Allied Tools
Compacting Factor Apparatus, 2 Nos of Trowel, 1 No of Scoop of adequate size, Tamper (16 mm in diameter and 600 mm length), Ruler, etc
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Fig. 3: Schematic of Compaction Factor Apparatus
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3. reference
IS 1199(Part 2):(First Revision) 2018 Fresh Concrete— Methods of Sampling, Testing and Analysis. Part 2-Determination of Consistency of Fresh Concrete
4. procedure
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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.
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Certain mixes have a tendency to stick in 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
shall be covered by the trowels.
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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 of concrete remaining
above the level of the top of the cylinder shall then be cut off by
holding a trowel in each hand, with the plane of the blades horizontal,
and moving them simultaneously one from each side across the top of
the cylinder, at the same time keeping them pressed on the top edge
of the cylinder.
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The outside of the cylinder shall then be wiped clean. The above operation shall be carried out at a place
free from vibration or shock. The weight of the concrete in the cylinder shall then be determined to the nearest 50 g.
This weight shall be known as the weight of partially compacted concrete.
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The excess of concrete remaining above the level of the top of the cylinder shall then be cut off by
holding a trowel in each hand, with the plane of the blades horizontal, and moving them simultaneously
one from each side across the top of the cylinder, at the same time keeping them pressed on the top
edge of the cylinder. The outside of the cylinder shall then be wiped clean. This entire process shall be
carried out at a place free from vibration or shock.
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This weight shall be known as the weight of partially compacted
concrete. The cylinder shall be refilled with concrete from the
same sample in layers approximately 5 cm deep, the layers being
heavily rammed or preferably vibrated so as to obtain full compaction.
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The top surface of the fully compacted concrete shall be carefully
struck off level with the top of the cylinder. The outside of the cylinder
shall then be wiped clean.
5. observation and recording
The compacting factor is defined as the ratio of the weight of partially compacted concrete to the weight of fully
compacted concrete. It shall normally be stated to the nearest second decimal place.
Sr. No. |
Description |
Sample 1 |
Sample 2 |
Sample 3 |
1 |
Weight of Empty Cylinder (W1) |
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2 |
Weight of Empty Cylinder + Free Fall Concrete(W2) |
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3 |
Weight of Empty Cylinder + Hand Compacted Concrete (W3) |
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4 |
Weight of Partially Compacted Concrete(WP = W2 - W1) |
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5 |
Weight of Fully Compacted Concrete(WF = W3 - W1) |
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6 |
Compaction Factor = WP/ WF |
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Table 1: Compaction Factor Test
6. Result
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Compaction Factor of Concrete is found out to be = .............
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The vertical difference between top of the mould and the displaced original center of the top surface of the specimen ………… mm
Workability |
Compaction Factor |
Slump (mm) |
Very Low |
0.78 |
0 - 25 |
Low |
0.85 |
25 - 50 |
Medium |
0.92 |
50 - 100 |
High |
0.95 |
100 - 175 |
Table 2 :Relation between Workability and Slump