Concrete Compaction Factor Test for Checking Workability

The compacting factor test is carried out in the laboratory as well as in the field. It is specifically conducted for concrete mixes of very low workability and generally utilized when concrete should be consolidated with vibration.

The method is suitable for plain and air-entrained concrete, that is formed with lightweight, normal weight or heavy aggregates with a nominal maximum size of 38 mm or less but not to aerated concrete or no-fines concrete.

Necessary Apparatus:

1. Balance: Balance should have the capacity to weigh upto 1 g.

2. Compaction Factor Apparatus with Allied Tools: Compacting Factor Apparatus, Trowel, Scoop about 150 mm long, Tamper (16 mm in diameter and 600 mm length), Ruler, etc.

Method:

1. The sample of concrete ready for testing should arranged softly in the upper hopper with the help of the hand scoop. The hopper should be filled level by its brim and the trap-door should be opened in order that the concrete pours into the lower hopper.

2. Certain mixes may be pasted in one or both of the hoppers. To get rid of this problem, the rod should be driven gently into the concrete from the top. Throughout this process, the cylinder shall be covered with the trowels.

3. When the concrete has come to rest instantly, the cylinder should be exposed, the trap-door of the lower hopper opened, and the concrete can be dropped into the cylinder. The excess of concrete that exists over the level of the top of the cylinder should then be cut off by using a trowel in each hand, with the plane of the blades horizontal, and shifting them concurrently one from each side across the top of the cylinder, simultaneously retaining them pressed on the top edge of the cylinder.

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4. The exterior of the cylinder should be wiped clean. It should be performed at a place without any vibration or shock. The weight of the concrete in the cylinder should then be set to the nearest 10 g.

5. The excess of concrete exists over the level of the top of the cylinder should then be cut off by retaining a trowel in each hand, with the plane of the blades horizontal, and shifting them concurrently one from each side across the top of the cylinder, simultaneously retaining them pressed on the top edge of the cylinder. The exterior of the cylinder should then be wiped clean. The whole process should be accomplished at a place without any vibration or shock.

6. This weight should be defined as the weight of partially compacted concrete. The cylinder should be refilled with concrete from the similar sample in layers roughly 5 cm deep, the layers should be greatly rammed or vibrated if possible in order to obtain full compaction.

7. The top surface of the fully compacted concrete should be cautiously struck off level with the top of the cylinder. The exterior of the cylinder shall then be wiped clean.

Observation And Recording: The compacting factor is known as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete. It shall generally be indicated to the nearest second decimal place.