How do we construct things in water? Things like bridges or roads that need support pillars that go into the water. If they’re made from concrete, how does the concrete ever dry if it’s underwater? If it’s in the ocean, does the very bottom of the pillar touch the seafloor?
In: Engineering
Concrete curing is a chemical reaction that actually requires water to complete, although excess water in the mixture can yield a weaker cured concrete. Special concrete mixtures are used which are more resistant to chlorides (when pouring in seawater), and care is taken not to agitate an underwater concrete pour too much so that the mix doesn’t thin out. You don’t need concrete to dry to cure it. In fact, keeping a pour damp throughout the curing process will generally lead to a more complete cure, because the process generates heat that can evaporate water away from the surface, leading to slightly weaker concrete at the surface. Underwater you don’t have that problem, though you do need to take care to keep the concrete and the surrounding water at its surface from being agitated and intermingling too much.
Bridge pillars and the like are often constructed using caissons, which is like a waterproof shoring form that extends to the riverbed / seabed, and then has all the water pumped out so that dry construction techniques can be used.
Usually they build caissons, which are temporary dams that seal to the bottom or to a sealed bottom of some sort, then they pump out the water. That’s not absolutely necessary, however, as concrete can be poured under water and will cure under water just fine. It’s the people that don’t like being under water.
In addition to the information of about concrete setting already posted quite a bit of that sort of thing is made from steel. Water doesn’t interfere with bolts clamping and welding underwater is commonly done.
For shallower waters things are often constructed on land then lowered into the water where they sit on or are driven into the ground under the water.
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