Under-Water Concreting work

★Underwater  Concreting

Inspection of concrete during placement in underwater concrete is difficult.

Therefore it is  essential to evaluate the proposed mix proportions.

Underwater concrete should have a slum 100 to 180 mm

Water cement ratio should not exceed 0.6 and may need to be smaller.

Maximum aggregate particle size is 40 mm

The cement shall be at least 350 kg per cubic metre of concrete.

Cofferdams shall be sufficient tight to ensure still water is applicable.

And in any case to reduce the flow of water to 3 metre per minute through the space into which concrete is to be deposited.

Cofferdams in stillwater shall be sufficient tight to prevent loss of motor through the walls.

Dewatering by pumping shall not be made which concrete is being placed or until 24 hours thereafter, otherwise it may be disturb the concrete and may lead to  undesirable results.

Concrete cast underwater shall not fall freely through the water.  otherwise IIT main leached and become segregated.

Concrete shall be deposited by continuously until it is brought to the required height.

† The methods to be used for depositing concrete underwater celibate taken one of the following..

  1. Tremie
  2. Direct placement with pumps
  3. Drop bottom bucket
  4. Bags
  5. Grouting

The void content of the coarse aggregates should be kept as low as possible.
The code assume a maximum void content of 55%…
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