Concrete Type for Bridge
Name: Jenni O.
What type of concrete is used for the underwater
structures of any bridge?
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.
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.
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Update: June 2012