Methods of depositing concrete in underwater.
In this article we will discuss one of the depositing concrete method in underwater.
The underwater concreting technique Design mostly to prevent cement washout.
★ Tremie
Underwater concreting using Tremie method is convenient for pouring large amount of high flowable concrete.
The tremie concrete placement method uses a vertical or near vertical pipes, through which the concrete is placed by gravity feed below water level.
# Procedure :-
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In this method a tremie pipe is inserted in the water up to the point where concrete is going to place.
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Generally the diameter of a tremie pipe varies from 20 cm to 30 cm.
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Depending upon the depth of concreting underwater we can add more tremie pipes by coupling it with one another.
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Before inserting the tremie pipe into the water the bottom end of the tremie pipe must be closed with a plug or thick polythene sheet or other suitable material.
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After tremie pipe reaches at the desired depth, of funnel is fitted to the top end of the tremie pipe to facilitate pouring of concrete.
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Then concrete having a very high slump of about 150 mm to 200mm is poured into the funnel, until the whole length of tremie pipe is filled up with concrete.
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Then the tremie pipe is lifted up and give a slight Jerk by a winch and Pulley arrangement.
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Due to all applications of jerk and weight of the concrete inside the pipe, the bottom plug fall and the concrete gets discharged.
( at this stage make sure that the end of the tremie pipe remains inside the concrete, because this will prevent entering of the water into the pipe from the bottom. )
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When all of the concrete inside the pipe gets discharged, the pipe is given again completely filled with concrete and the process is repeated.
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This process of filling and discharging of concrete is repeated without any interruption, until the concrete level come over the water table .
‡‡ Design concepts and tricks provided tips :-
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No compaction is required for underwater concreting, as concrete gets contacted by the hydrostatic pressure of water.
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Pumping of water should not be allowed while concreting, because it may suck cement particles from the concrete.
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