Compaction Factor Test is
designed in such a way that it can be used only in laboratory but in some
cases, it can be used for field concrete tests. The compacting factor test has
been developed at the Road Research Laboratory in United Kingdom. This test is
one of the most accurate test performed in order to determine the workability
of concrete.
AIM: To determine the workability by compacting factor test.
APPARATUS:
- Compaction factor testing machine,
- Trowels,
- Hand scoop (15.2 cm long),
- Standard tamping rod (1.6 cm diameter, 61 cm long rounded at one end),
- balance.
FIGURE:
THEORY:
This is defined as the ease with which concrete can be compacted fully
without Segregating and bleeding. It can also be defined as the amount
of internal work required to fully compact the concrete to optimum
density. The workability depends upon the quantity of water, grading,
shape and the percentage of the aggregates present in the concrete.
To test the workability of freshly mixed concrete,
compaction factor test is carried out. This test works on the principal of
determining the degree of compaction achieved by standard amount of work done
by allowing the concrete to fall through a standard height. The degree of
compaction factor is the ratio of weight partially compacted concrete to the
weight of fully compacted concrete.
Dimensions of Compaction factor testing machine:
Description
|
Dimension CM
|
Upper Hopper, A
|
|
Top Internal Diameter
Bottom Internal Diameter
Internal Height
|
25.40
12.70
27.90
|
Lower Hopper, B
|
|
Top Internal Diameter
Bottom Internal Diameter
Internal Height
|
22.90
12.70
22.90
|
Cylinder, C
|
|
Internal Diameter
Internal Height
|
15.20
30.50
|
Distance between bottom of upper hopper and
top of lower hopper
|
20.30
|
Distance between bottom of lower hopper and top of cylinder
|
20.30
|
PROCEDURE:
1. Ensure the apparatus and associated equipment are clean before test and
free from hardened concrete and superfluous water.
2. Weigh the bottom cylinder to nearest 10gm, put it back on the stand and
cover it up with a pair of floats.
3. Gently fill the upper hopper with the sampled concrete to the level of the
rim with use of a scoop.
4. Immediately open the trap door of the upper hopper and allow the sampled
concrete to fall into the middle hopper.
5. Remove the floats on top of the bottom cylinder and open the trap door of
the middle hopper allowing the sampled concrete to fall into the bottom cylinder.
6. Remove the surplus concrete above the top of the bottom cylinder by holding
a float in each hand and move towards each other to cut off the concrete across
the top of cylinder.
7. Wipe clean the outside of cylinder of concrete and weigh to nearest 10gm.
8. Subtract the weight of empty cylinder from the weight of cylinder plus
concrete to obtain the weight of partially compacted concrete.
9. Remove the concrete from the cylinder and refill with sampled concrete in
layers.
10.Compact each layer thoroughly with the
standard Compacting Bar to achieve full compaction.
11.Float off the surplus concrete to top of
cylinder and wipe it clean.
12.Weigh the cylinder to nearest 10gm and
subtract the weight of empty cylinder from the weight of cylinder plus concrete
to obtain the weight of fully compacted concrete.
13.The compacting factor (CF) = (weight of
partially compacted concrete) divided by (weight of fully compacted concrete).
RESULTS AND ANALYSIS:
Weight of the Empty Cylinder, W
Weight of the Partially Compacted Concrete, W1
Weight of the Fully Compacted Concrete, W2
Compacting Factor, (C.F) =(W1-W/W2-W)
CONCLUSION:
Value Of Compacting Factor
|
Standard Of Workability
|
0.95
|
Good
|
0.92
|
Medium
|
0.85
|
Low
|
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ReplyDeletenice explanation about compaction factor test
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