[TheJoeMan]

Even structural items can be made quite thin! There is a college design competition to make concrete canoes which can be 3/8" to 7/16" thick: https://www.concretecanoe.org/2008Triva/Florida2008DesignPap...

[chasd00]

oh wow that takes me back. I remember touring, i think it was Texas A&M, in HS and they showed off their "concrete canoe" to the group. This would have been in the late 1900s.. 1995 or around there.

[lostlogin]

There have been ships made of concrete.

https://en.wikipedia.org/wiki/Concrete_ship