What Is Underwater Concreting? | Know 5 Methods Of Underwater Concreting Here - Civil Giant (2023)

Table Of Contents

  1. Methods for Underwater Concreting
  2. 1. Tremie Pipe Method
    • What is a tremie pipe?
    • Components used in tremie pipe method
    • Slump of the concrete to be used in tremie pipe method
    • Procedure for concreting by tremie pipe method
    • Advantage of tremie pipe method
    • Drawback in using tremie method
  3. 2. Bottom Dump Bucket Concreting
    • Steps for the method
    • Drawback of bottom dump bucket concreting
  4. 3. Method of Depositing Bags of Dry or Semidry Mix of Concrete Materials below Water
    • Steps for the method
    • Drawback of the method
  5. 4. Grouting Process of Pre-Packed Aggregates
    • Steps for this method
  6. 5. Placing of Concrete with Use of Pipes and Concrete Pumps
    • Steps for the method
  7. Precautions to be Taken While Placing Concrete Underwater
  8. Key Takeaway
    • FAQ

Underwater concreting is the process of placing concrete under water for any purpose.

Many times structures are to be constructed partially or fully underwater. For example, marine structures, bridges over water bodies, well foundations, etc.

Underwater concreting methods are to be used for concreting when concreting is to be done well underwater or in a trench filled with bentonite slurry.

The few methods to be used for underwater concreting are as listed below;

  • Bottom dump bucket concreting
  • Method of depositing bags of dry or semidry mix of concrete materials below the water
  • Tremie pipe method
  • Grouting process of pre-packed aggregates
  • Placing of concrete with the use of pipes and concrete pumps

Above mentioned methods are explained in detail below in the article.

The word tremie was derived from a French word that meant hopper.

This method can be considered the only satisfactory method for underwater concreting.

What is a tremie pipe?

  • Tremie pipe is a pipe with a diameter of about 20 centimeters.
  • It is capable of easy coupling in case of an increase or decrease in length.

Components used in tremie pipe method

The components used in the tremie method are listed below;

  • Funnel
  • Tremie pipe
  • Winch and pully arrangement
What Is Underwater Concreting? | Know 5 Methods Of Underwater Concreting Here - Civil Giant (1)

Slump of the concrete to be used in tremie pipe method

The concrete to be used in the tremie pipe method should have a very high slump of about 15 to 20 centimeters.

Procedure for concreting by tremie pipe method

The procedure to place concrete underwater with the tremie pipe method is written below;

  • The top of the tremie pipe is fitted with a funnel to facilitate the pouring of concrete in it.
  • Plugs, polyethylene sheets, or such materials are used to close and block the bottom end of the tremie pipe.
  • The tremie pipe is then taken below water and toward the place where concreting is to be done.
  • The tremie pipe is then made to rest at the point where concrete is going to be poured.
  • As before the bottom end was plugged already the water can’t get into the tremie pipe.
  • The fresh concrete is then poured into the funnel.
  • The tremie pipe is lifted up when it is fully filled up with concrete and given a slight jerk by a winch and pully arrangement.
  • As the pipe is raised and jerked slightly, due to the heavy weight of concrete the plug at the bottom of the pipe falls, and concrete is discharged from the tremie pipe.
  • Particular care should be taken to make sure that the bottom end of the tremie pipe remains inside the concrete.
  • It is done to make sure the water can’t enter from the bottom of the tremie pipe.
  • It can be said that the tremie pipe has still remained plugged at the bottom end by concrete.
  • After that again the process is repeated from filling concrete in the tremie pipe through the funnel to the deposition of concrete from the tremie pipe by giving it a slight jerk.
  • Again it should be made sure that during the whole process the bottom end of the tremie pipe remains in concrete.
  • In this way, the process is repeated again and again continuously till the level of concrete is above the water level.

Advantage of tremie pipe method

There is an advantage to using the tremie method over other methods for underwater concreting.

The concrete does not get affected by water except for the top layer in contact with water. Also, the top layer can be scrubbed or cut off at the end of the whole operation to remove the affected concrete.

Drawback in using tremie method

This method requires high-consistency concrete. This needs a high w/c ratio.

And these in turn reduce the strength of concrete.

Though in present times, because of the usage of superplasticizers it is not a drawback anymore.

Now concrete having a very low w/c ratio of 0.3 or even less can be placed by using the tremie method.

This method is done using a watertight box or bucket. This can also be called as bucket method of underwater concreting.

Steps for the method

The steps of this method are written below;

  • Concrete is taken to the place of concreting by a water-tight box or bucket.
  • Reaching the place for deposition, the bottom of the box or bucket is opened by the use of some mechanism.
  • Whole concrete is then dumped carefully and slowly.

Drawback of bottom dump bucket concreting

In this method, because a certain amount of washing away of cement is bound to happen, it does not gives satisfactory results in strength.

No special equipment or mechanisms are needed for this method. It is a crude and simple method of underwater concreting.

Steps for the method

The steps for this method are as written below;

  • First dry or semidry mix of cement, fine aggregates, and coarse aggregates are filled in cement bags.
  • Such bagged concrete mix material is then deposited on the bed below the water.
  • There it comes in contact with water and cures, hence hardening takes place.

Drawback of the method

In this method, because only dry or semidry mix materials are put in gunny bags and directly put under water voids will be formed in the resulting concrete mass. This will not give the satisfactory results needed.

This is a method that is not commonly employed for underwater concreting.

It is mostly adopted when plugging well foundations though.

Steps for this method

The steps for this method are explained below;

  • For this method to work, first coarse aggregates are dumped at concreting place to assume the full dimensions of the concrete mass.
  • Then the cement mortar grout is injected through pipes, which are extended to the bottom of the aggregate bed made before.
  • As the grouting process progresses the pipes are slowly withdrawn.
  • The cement grout forces out the water from interstices and occupies that space instead.

This is another method that can be used to place concrete underwater.

This method makes use of pipes and concrete pumps to place concrete on an underwater bed.

Steps for the method

Steps for this method are described below;

  • The pipeline is plugged or blocked at one end and that end is lowered until it reaches the concreting place at the bottom.
  • After resting the pipe end at the designated point pumping of the concrete is started.
  • Once the pipe is fully filled with concrete the plug at the bottom is forced out.
  • It should be made sure that the pipe end remains in the concrete as now the concrete surrounding the bottom end of the pipe acts as a plug and seals it from water.
  • The pumping is done against the pressure of the plug at the bottom end.
  • As the operation progresses, once the pumping effort required to overcome pressure becomes too great the pipe is withdrawn and the operation is repeated again.
  • This repeated process continues till the concrete reaches the level above the water surface.

As pipelines are used, a very common issue faced if of blockage. To know how to tackle this, READ Blockage of Concrete Pipelines.

Underwater concreting demands care while placing concrete. That is tabulated below;

PrecautionsReason
Pumping of water should not be done during the process of placing concrete underwater.Cement particles may get sucked with water if simultaneous pumping is done.
Underwater concrete does not need to be compacted and compacting equipment shouldn’t be used.The concrete gets automatically compacted by the hydrostatic pressure of water also, the consistency of concrete is such that it does not normally require compaction

Definition: Underwater concreting is the process of placing concrete under water for any purpose.

There are a few methods that can be used to place concrete underwater.

Bottom dump bucket concreting

In this method, a watertight box or bucket is used to carry concrete to the bed and a bottom opening mechanism is used to gently dump the concrete in the place.

Method of depositing bags of dry or semidry mix of concrete materials below the water

In this method, as the name suggests bags filled with a dry or semidry mix of concrete materials are placed below water.

Tremie pipe method

This is the method that uses a tremie pipe to place concrete below the water.

Grouting process of pre-packed aggregates

In this method, coarse aggregate is placed in size equal to concrete mass and then cement grout is filled in gaps with the pipes.

Placing of concrete with the use of pipes and concrete pumps

In this method, concrete is placed with help of pipes and concrete pumps.

Precautions to be taken while placing concrete underwater

  • Pumping of water should not be done during the process of placing concrete underwater.
  • Underwater concrete does not need to be compacted and compacting equipment shouldn’t be used.

FAQ

What is underwater concreting method?

Underwater concreting method is a way to place concrete below water.

Which method is used for underwater construction?

Underwater concreting methods are as listed below;

  • Bottom dump bucket concreting
  • Method of depositing bags of dry or semidry mix of concrete materials below the water
  • Tremie pipe method
  • Grouting process of pre-packed aggregates
  • Placing of concrete with the use of pipes and concrete pumps

What type of concrete is used for underwater?

Concrete having a very high slump of 15 to 20 centimeters only can be used in the tremie method for underwater concreting.

What is tremie method?

Tremie method is the method that uses a tremie pipe to pour concrete to the designated place in a way that does not allow wash out of cement from the concrete.

How underwater construction is done?

Underwater construction can be done by using the following methods;

1. Bottom dump bucket concreting:

In this method, a watertight box or bucket is used to carry concrete to the bed and a bottom opening mechanism is used to gently dump the concrete in the place.

2. Method of depositing bags of dry or semidry mix of concrete materials below water:

In this method, as the name suggests bags filled with a dry or semidry mix of concrete materials are placed below water.

3. Tremie pipe method:

This is the method that uses a tremie pipe to place concrete below the water.

4. Grouting process of pre-packed aggregates:

In this method, coarse aggregate is placed in size equal to concrete mass and then cement grout is filled in gaps with the pipes.

5. Placing of concrete with the use of pipes and concrete pumps:

In this method, concrete is placed with help of pipes and concrete pumps.

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