Sunday, February 22, 2009

Underwater concrete

Placing of concrete in water is a very difficult operation all aspects from mixing transportation placing and control of the work have to be carefully evaluated and should only be preformed be very experienced engineers and workers the aim in placing concrete underwater is to keep the fresh concrete and water a part as much as possible during the placing of the concrete, and to avoid a rapid flow of either of them and when they come in contact. So that cement will not be washed out.
For this reasons, the correct placing method is the most important factor with respect to final quality.

Underwater concreting is not a new technique: it has been experimented with since about 1850. In 1910 the Norwegian August Gunderson, took a Norwegians patent on a method of underwater casting for concrete columns and the like. In the same year, the method was tried for the first time In Norway for underwater concreting of reinforced structure. This method is, nowadays, the Maine underwater concreting method and is known as termite pipe method.

Since 1980s, admixtures that increase the cohesion of the concrete and make direct contact with water passable without signification changing the properties of the concrete have been developed and are widely used. The ant washed out (AWO) admixtures.

E.g. Rescan T from Norway and similar product, has certain properties that influence the fresh concrete, and the setting and hardening of it knowledge about this properties
is crucial for all parties involved.

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