What is Underwater Concreting?

Underwater concreting is a critical concreting process performed for offshore construction. It involves the process of carefully placing fresh concrete underwater. As construction in water results in many difficulties, the start to end of an underwater construction requires special care, supervision and planning. For example, the construction of the foundation and piles to support the bridge crossing a river, or a dock construction. 

Fig.1. Underwater Concreteing; Image Courtesy: https://menafn.com/

The main objective of any underwater construction project is to create a sry and water free environment to safely place and cure concrete that helps to give a structurally stable and durable structure.

The two important know how on underwater concrete construction are:

1. Underwater Concrete

2. Underwater concreting methods and techniques

1. Underwater Concrete

The underwater concreting involves mixing the concrete on the surface in the conventional manner and then placing this underwater by various methods. A properly mixed concrete is a stable material that when dried gains twice the density of water and remains unaffected by water. During the process, the concrete is immersed and allowed to set by providing it a drying environment. 

There are many risks associated with the vibration and levelling of the concrete placed underwater. The concrete can be washed out in situations of placing. So, some anti-washout admixtures and placing techniques must be employed.

2. Underwater Concreting Techniques and Methods

The various underwater construction methods are:

1. Tremie method

2. Grouting method

3. Using bags

4. Bucket placing

5. Pre-placed aggregate method

6. Pumping

The various underwater construction techniques is by using caissons and cofferdams

Applications of Underwater Concreting

1. To construct footing block in water to support  structures

2. To tie various elements in composite action

3. To fill the pre-excavated holes in the seafloor to act as a leveling mat

4. To construct solid ballast to add weight and lower the centre of gravity

5. To fill the base of gravity platform to obtain uniform bearing and provide shear transfer

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