Tremi Method of Underwater Concreting

The most accepted method of underwater concreting is the Tremi method.

In this method a tremie pipe is inserted into the water to the point where the concrete is being laid. Generally the diameter of a tremie pipe varies from 20 cm to 30 cm. Depending on the depth of the concreting under water we can add more tremie pipes interconnecting it.

Before inserting the tremie pipe into the water, the lower end of the tremie pipe should be closed with a plug or thick polythene sheet or other suitable material.

After the tremie pipe reaches the desired depth, a funnel is attached to the top end of the tremie pipe, to facilitate pouring of concrete.

Then concrete with a very steep slope of about 150 mm to 200 mm is poured into the funnel until the entire length of the tremie pipe is filled with concrete.

The tremie pipe is then raised and given a slight blow by a pulley and pulley arrangement. The weight of the concrete and jerking inside the pipe causes the bottom plug to collapse and the concrete to discharge.

At this stage, Make sure the end of the tremie pipe remains inside the concrete, as this will prevent water from entering the pipe from below.

When all the concrete inside the pipe is discharged, the tremie pipe is again completely filled with concrete and the process is repeated. This process of filling and dropping the concreting is repeated without interruption, until the level of the concrete rises above the water level.

notes

Pumping of water should not be allowed while concreting, as it may suck the cement particles from the concrete.
Underwater concreting does not require any compaction, as the concrete becomes compacted by the hydrostatic pressure of the water.