Tremie concreting

It is the easiest process to set concrete under the water with the help of tremie pipe. The origin of the word tremie is from the French word hopper.

Tremie process

• A tremie belongs to a pipe with strong water resistance capacity.
• Normally, its diameter remains 250mm.
• There is funnel shaped hopper at its upper side and a loose plug at the lower side.
• It stands on a working platform over water level.

Process of tremie concreting

A tremie pipe with 200mm to 250mm diameter is utilized. With the use of coupling, the length of pipe is raised or reduced. There is a funnel at the top end of pipe so that the concrete can be poured easily. The lower end is concealed with a plug or solid polyethylene sheet to resist water penetration into the pipe. The pipe goes down and rests at the point where the concrete should be arranged. The concrete with an extreme slump of about 15 to 20 cm is poured into the funnel. As soon as the entire length of pipe is stuffed with the concrete, the tremie pipe is upriased and with a little tweak the plug is driven out and the concrete is released.

Once the concreting begins, the lower side of the tremie should be intensely immersed in the concrete that is set earlier to resist penetration of water into the pipe from bottom side. The tremie should be upraised gradually so that the concrete does not outflow, precautions should be taken to keep the seal tight at the bottom. Thus, the concreting is continued ceaselessly unless the concrete level is visible over the water level.

The following preventive measures should be kept throughout concreting with tremie method:-

• Cofferdams or forms should be properly fixed to minimize the flow of water under 3m per minute through the space being concreted.
• All the time, the lower side of the tremie pipe should be properly implanted in the wet concrete.
• As soon as the concreting is commenced the tremie should not be placed transversely through the stored concrete so that the concrete remains unaffected. If is required to move the tremie. It should be upraised and brought to the new position.

• Restrain from pumping of water at the time of placing the concrete. If pumping is done concurrently, it may absorb the cement particles.
• Under water concreting should never be compacted since the concrete is automatically compacted with the hydrostatic pressure of water.
• There should be greater water ratio to retain extreme consistency that minimizes the concrete strength. But the super plasticizers can help to place a concrete with very low water ratio as 0.3.
• In case heavy quantities of concrete are essential for being arranged over a widespread area, tremies should be applied.