COMPACTION FACTOR TEST

(IS: 1199-1959)

OBJECT:

To determine the workability of concrete mix of given proportion by compaction factor test.

APPARATUS:

Compaction factor apparatus, trowel weighing machine conical hoppers mounted vertically above the cylindrical mould. The upper mould has internal dimensions as top dia 25 cm bottom dia 12.5 cm and height 22.5 cm. The lower hopper has internal dimensions, top 22.5cm bottom dia 12.5cm and height 22.5cm. The cylinder has internal dimensions as 15 cm dia and 30cm height. The dimensions between bottom of the upper hopper and top of the lower hopper, bottom of the lower hopper and top of cylinder are 20 cm, each case. The lower ends of the hoppers are filled with quick release trap doors.

THEORY:

This test is adopted to determine workability of concrete where nominal size of aggregate does not exceed 40 mm. It is based on the definition, that workability is that property of concrete, which determines the amount of work required to produce full compaction. The test consists essentially of applying a standard amount of work to standard quantity of concrete and measuring the resulting compaction. The compaction factor is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete. It shall be stated to the nearest second decimal place.

PROCEDURE:

Conduct test for W/c ratio 0.5, 0.6, 0.7, and 0.8, for each mix take 10 kg of coarse aggregate 5kg of fine aggregate and 2.5 Kg of cement.

1. Grease the inner surface of the hoppers and the cylinder.

2. Fasten the hopper doors.

3. Weigh the empty cylinder accurately (Wt. Kgs).

4. Fix the cylinder on the base with fly nuts and bolts

5. Mix coarse and fine aggregates and cement dry until the mixture is uniform in colour and then with water until concrete appears to be homogeneous.

6. Fill the freshly mixed concrete in upper hopper gently with trowel without compacting.

7. Release the trap door of the upper hopper and allow the concrete of fall into the lower

hopper bringing the concrete into standard compaction.

8. Immediately after the concrete comes to rest, open the trap door of the lower hopper and allow the concrete to fall into the cylinder, bringing the concrete into standard compaction.

9. Remove the excess concrete above the top of the cylinder by a trowel.

10. Find the weight of cylinder i.e cylinder filled with partially compacted concrete (W2).

11. Refill the cylinder with same sample of concrete in approx. 4 layers, tamping each layer with tamping for 25 times in order to obtain full compaction of concrete.

12. Level the mix and weigh the cylinder filled with fully compacted concrete (W3 Kg)

13. Repeat the procedure for different for different a trowel.

OBSERVATIONS AND CALCULATIONS:

Weight of cylinder = W1 Kgs.

S.No	W/c ration	W/c ration Wt. With partially compaction W2 (Kgs)	Wt. With Fully compaction W3 (Kgs)	Wt. With partially compacted concrete (W2- W3) (Kgs)	Wt. With fully compacted concrete (W3- W1) (Kgs)	Compaction factor (W1- W2)/ (W3- W1)
1.
2.
3.

RESULT:

PRECAUTIONS:

1. The top hopper must be filled gently.

2. The mix should not be pressed or compacted in the hopper.

3. If the concrete in the hopper does not fall through when the trap door is released, it should

be freed by passing a metal rod. A single steady penetration will usually affect release.

COMMENTS:

It is more sensitive, precise than slump test and is particularly useful to concrete mixes of low workability.

Suggested ranges of values of compaction factors for different placing conditions.

S.No	Placing condition	Degree of workability	Values of workability
1.	Concreting shallow section with vibration	Very low	0.75 to 0.80
2.	Concreting of lightly reinforced section with vibration	Low	0.8 to 0.85
3.	Concreting of lightly reinforced section Medium without vibration or heavily reinforced with vibration	Medium	0.85 to 0.92
4.	Concreting of heavily reinforced section without vibration	High	0.92 to above

Practical knowledge of civil engineering

Thursday, December 3, 2020