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Name: Jenni O.
Status: Student
Age: 16
Location: N/A
Country: N/A
Date: 2002
Question:
What type of concrete is used for the underwater structures of any bridge?


Replies:
Jenni:

Although some adjustments in the concrete proportions have to be made for underwater placement, generally no truly special type of concrete is needed. Many people have the misconception that concrete must "dry" to harden. In fact, concrete must be kept wet to reach its full strength. The portland cement in the concrete requires water to complete the chemical reaction that makes it hard. If concrete is allowed to dry after placement, it will not reach the same strength as a concrete that is kept wet or covered with a "curing compound" that seals moisture inside. So, concrete will harden quite nicely underwater.

Andy Johnson

Dear Jenni,

The hardening of concrete is due to a chemical reaction and is not due to the presence or absence of water or air. Therefore concrete under water hardens exactly as it would above water.

Best, Dick...


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