This is super interesting, but why were we building concrete boats and are not doing it anymore? Was it more or less just a experiment?
In short it seems like a combination of high labor cost, high corrosion risk (concrete chips and salt water erodes the rebar inside) and technological advancement (fiberglass). Also the steel shortage that birth these in the first place was short lived.
Yep that. Plus the Mulberry harbours were designed specifically to be sunk to act as harbours and breakwaters, for which concrete is actually fairly well suited. We have other ways of building harbours during peacetime that don't involve sailing them across a large body of water though
Basically, no one would have ever started using concrete, if steel would have been more avaiable.
Fiberglass is super cheap and is what most boats are made out of now. Balsa wood core, fiberglass shell. Pennies compared to the cost of a concrete pour. Another issue is that concrete is porous so the rebar inside would rust faster.
In the end, there’s no reason why you can’t. There’s plenty of reason why you shouldn’t. Costs being the biggest. Fiberglass builds are just so much cheaper than anything before it.
Well, sort of we still are, there are competitions to build concrete boats
https://en.wikipedia.org/wiki/Concrete_canoe (also a thing in europe)
But not as commercial products. Because concrete is just not the best ship building material, you only use it if you either want the challenge (as a student) or you simply don't have anything better at hand.
This video came up in my feed yesterday, and in the end he makes a reference to Michael Lewis Moneyball and ”working within constraints”, the best with what they had when steel was scarce etc:
Concrete is not a good material to build ships. As a ship moves it goes over waves and is subject to forces that want to bend the hull. Steel flexes slightly, but concrete does not not. It becomes brittle over time and the ship breaks apart.