Compaction Factor Test for Fresh Concrete

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• Aim: To find out the compaction factor for the given fresh mix of concrete.

• Theory: Workability of concrete is the ability/ease with which concrete can be mixed, transported and placed. This is a major factor which contributes to the other properties of concrete also. If concrete is workable enough then it can be compacted with less compacting effort.

 So there is a relation between the amount of work required to compact a given fresh concrete and the work-ability of the concrete. This relation is well suited for the concrete of the low water cement ratio. Slump cone test is also used to find out the work-ability of the concrete but only recommended for the concrete of higher work-ability. For less workable concrete(having less water cement ratio), compaction is standardized by various standards. 

• Apparatus: Compaction factor apparatus/machine, weighing balance, cow/mixing tray.

Compaction Factor apparatus

• Procedure:

1. Oil the inner sides of the top and bottom cone frustum.

2. Prepare a M15 concrete mix(1:2:4) using a water content of about 0.4-0.6 by weight of cement.

3. Fill the top cone frustum with the fresh mix of concrete and then open the gate and let the concrete fall on the second frustum.

4. Open the gate of second frustum and let it fall on the cylinder to fill up to top of cylinder. 

5. Measure the weight of the cylinder filled with the concrete(partially compacted) and then empty this.

6. Again fill the cylinder with the same sample of the concrete but this time, do the compaction using the mechanical vibrator to do the compaction. 

7. Again measure the weight of the cylinder filled with the concrete(Fully compacted).

8. Clean all the apparatus and put them at their places as before.

• Calculations: 

Let weight of the empty cylinder = W1

Let weight of the cylinder with the partially compacted concrete = W2

Let weight of the fully compacted(Using mechanical vibrator) concrete with cylinder = W3

Compaction Factor = Weight of the partially compacted concrete/ Weight of the fully compacted concrete

i.e., Compaction factor = (W2-W1)/(W3-W1)

• Result: The compaction factor of the given fresh concrete mix is .....

(Note: Relation between the compaction factor and work-ability is that higher the compaction factor higher is the work-ability. Theoretical maximum value of the compaction factor can be 0.96 to 1.0)

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