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About Dams

Back to buildingBuilding a concrete dam

A concrete batching plant on the construction site for a gravity dam

A concrete batching plant on the
construction site for a gravity dam

As so much concrete is required in a concrete dam, it is mixed together in a special building called a concrete batching plant, which is built on the construction site. For very large dams, there may be a number of batching plants. The concrete can be placed in the dam by two different methods.

Pouring Concrete

The traditional method is to pour a wet mixture of concrete into a mould made in the required shape of the dam. The mould, called formwork, is usually made from sheets of timber. The mould is not made to the full height of the dam, as the dam is built upwards in stages of about 1 to 2 metres at a time. The concrete is left to dry before the next section is formed on top.

The concrete can be transferred from the batching plant to the dam by a number of methods. Sometimes, a system of conveyor belts is used and sometimes the concrete is taken by trucks to the bottom of the dam where it is poured into skips which are lifted to the top of the dam by cranes.

Concrete conveyorTruck SkipCrane Skip

Compacting Concrete with Rollers

Compacting concrete

Concrete being placed and compacted
on Stillwater gravity dam in the
United States

Roller Compacted Concrete (RCC) dams are formed by spreading a drier of mix of concrete and compacting it down using rollers. The dam is raised in steps of about 600 mm. The edges are formed first, by making low concrete walls on the upstream and downstream faces of the dam. Concrete is then transported to the area between the walls and spread in a thin layer using bulldozers. Rollers are then driven over the concrete to compact it down.