Underwater Concrete: Methods, Properties, Merits & Demerits

Underwater Concrete

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Underwater concrete is a construction material commonly used in all types of civil engineering works.

During the construction of bridges, dams or other construction where the bottom part of the structures is probably to lie underwater, we can use underwater concrete.

Many difficulties in water formation, especially in places where the depth is large; therefore proper mixing design, solid production, placement and quality control must be followed.

Methods of Underwater concrete:

1) Tremie method:

Tremie pipe is a satisfactory method of underwater concreting.

The tremie pipe is a pipe whose diameter is about 20 cm.

A funnel is mounted at the top end to facilitate concrete pouring.

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The lower end of the pipe is closed with a plug or thick polyethene sheet.

As the end of the vibrating pipe is blocked, no water will enter.

Concrete is poured over the funnel and when the entire length of the pipe is filled with the concrete, vibrating pipe is lifted up and given a slight shock.

Care must be taken while concreting, the lower end of the pipe is embedded in the well-wet concrete.

Concrete has a very high deceleration of about 15 to 25 cm.

Underwater Concrete with a low water/ cement ratio can be kept to 0.3 or even less.

2) Bucket Placing Method:

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This method has an advantage that concrete can be carried out at considerable depth.

The main disadvantage of the bucket method is the difficulty in keeping the upper surface of the placed concrete at a reasonable level.

3) Placing in bags Method:

In this method, gunny bags are partially filled with concrete and tying them in such a way that they can readily be accommodated on which they are placed.

4) Packed Concrete Method:

This method is also called grouted concrete.

This technique consists of placing the coarse aggregate only informs and thoroughly compacting it to form a preplaced mass.

This mass is grouted with cement mortar.

Properties of underwater concrete:

Maintenance process includes initial inspection, worsening prediction, inspection, evaluation and remedial measures.

During construction, social as well as economic aspects should be required along with engineering.

Adequate safety from corrosion can be achieved by using anticorrosion or protecting merchandise.

Spalling of concrete can be avoided by expanding the concrete carefully.

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Construction Techniques:

Caissons:

It is watertight retaining structure & permanent in nature.

Caissons are used in Bridges pier, the development of concrete dams or the repair of ships.

It is constructed in such a way that water can be pumped.

Underwater Concrete keeps working environment dry.

Cofferdam:

It is a temporary enclosure & built within a body of water or in piers.

The enclosed space permits for pumping, making a dry working environment.

Cofferdams are usually welded steel structures with sheet piles and cross braces components.

For dam construction, two cofferdams are normally constructed, one upstream and one downstream.

Advantages of underwater concrete:

  • It allows construction and excavation in a poor environment.
  • It provides a harmless environment for working.
  • Sheet piles are easy to install and remove.
  • The material can usually be reused on other projects.

Disadvantages of underwater concrete:

  • Rapidly rising water can eject the scour hole & it is one of the main fundamental causes of bridge failure.
  • Cracks, scaling, crazing and potting are very common in concrete.
  • Rebar is steel reinforcement bars that are passively located within the concrete, they undergo corrosion.
  • The concrete broke, flattened, or piled up due to poor installation and environmental factors.

Also, read 1. Roller Compacted Concrete 2. Polymer Concrete 3. Lightweight Concrete

Frequently Asked Questions:

What is underwater concrete?

Underwater concrete was designed specifically to increase construction efficiency and performance in water environments.

Which cement is used in underwater construction?

Portland cement

How do you fix concrete underwater?

Areas completely damaged by fresh water.
Apply a bandage coat.
Apply repair mortar before applying coat.
Apply a curing membrane to the applicable repair mortar.
Protect the repaired area against the action of the wave until it becomes sufficiently rigid.

Who invented underwater concrete?

The Roman Empire invented a unique marine concrete that allowed the construction of huge, durable structures – even underwater.

Conclusion:

For the wet development of navigation constructions, underwater concrete building is a crucial element.

Underwater concrete construction can be skilful with the same degree of consistency.

If construction just isn’t accomplished properly in water, then with correct concrete mixing and placement, it may results of the main overvaluation in construction prices and schedule.

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