Q: What is the difference between the concrete used in dry construction and
the one used underwater that solidifies in totally wet conditions?
A: There is no difference between the concrete used above and underwater.
The setting of concrete is a hydration process, and can only occur in the
presence of water.
If 鈥渄ry鈥� concrete is allowed to dry out before the curing process has
finished, the concrete will be weak. For this reason, concrete slabs with a
large surface area are often covered with a polythene sheet to slow down
evaporation. Concrete underwater only requires protection to prevent it being
washed away or diluted. In certain circumstances special concretes may be
required, such as sulphate-resistant concrete for use in seawater.
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