One of the more interesting materials proposed for shipbuilding to save steel, was ice/sawdust. Apparently not quite as impractical as it sounds.

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

I had no idea we used concrete ships during WWII until I found out we sunk one during the atomic testing in the Pacific.

The US used a concrete ship (YO-160) [1] as one of the target/target vessels during the Operation Crossroads tests [2]. The ship had been used as an oiler/fuel barge during WWII and sunk not from the tests directly but from damage sustained when moving it after the Able test. Although the Baker shot served as a coup de grâce (ultimately sinking the vessel), YO-160 was already taking on water and probably would have sunk on its own.

[1] https://en.wikipedia.org/wiki/YO-160

[2] https://www.youtube.com/watch?v=xGQkTDStnx0&t=22m36s

The Seasteading Institute had some pages about concrete oceanic structures that captured my imagination a while back https://www.seasteading.org/2010/11/green-float-the-botanica... https://www.seasteading.org/2010/05/cocrete-structures/

They are not "boats" exactly!

The half-sunken SS Atlantus used to be quite visible off of Sunset Beach in Cape May, New Jersey. It's been steadily sinking over the years and not much is visible from shore anymore. Here's a view, probably from the sixties:

http://www.concreteships.org/ships/ww1/atlantus/postcard-bre...

Slightly tangentially, there's a great short documentary on the building of Chevron's Ninian Central Platform at Loch Kishorn in 1978 [0]. At the time of construction it was the largest "man-made movable object". The base and supporting column for the drilling platform itself was constructed entirely out of concrete and floated to ~100 miles north east of the Shetlands.

Really is quite amazing that you can float a 600,000 tonne object several hundred miles out to sea.

[0]: http://movingimage.nls.uk/film/5973

[1]: https://en.wikipedia.org/wiki/Loch_Kishorn#Kishorn_Yard

[2]: https://en.wikipedia.org/wiki/Ninian_Central_Platform

Nice article, but note that the site's operator is "on pause in 2017", and the video appears to pre-date the damage sustained by the SS Palo Alto during winter storms of January, 2017.

https://www.washingtonpost.com/news/morning-mix/wp/2017/01/2...

For more concrete fun, and interesting material sciences challenges, see what floats civil engineering students' boats: http://www.asce.org/event/2017/concrete-canoe/

Reminds me of the Mulberry harbours from DDay

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

As kids back in the 60s, we loved to climb all around that ship when we'd camp in the park. It is amazing to me that we never got hurt or fell into the ocean, given there were holes in the deck that weren't fenced off. Rusted, flaking metal was all around, waiting to slice open a hand or a foot but, somehow, we survived. I never knew, until now, 50 years later, the history of that ship or its name.

There's good information available on the early 20th C concrete tugs built in Britain which that article glosses over. Three are visible near the mouths of various Irish and English rivers.

http://www.worldnavalships.com/forums/archive/index.php/t-14...

I was just talking to my SO about the cement ship the other day. Not really so much about the ship itself, but the fact the pier is suffering the same fate as the ship. It was once a rather big fishing spot when I was growing up, but not it is completely closed off. Once it's gone it isn't going to be rebuilt.

I grew up a few miles from the beach with the row of concrete ships sunken at Kiptopeake, Virginia that is pictured in the article.

Crappy ships, but they are fantastic artificial reefs. We used to kayak or boat right next to them and catch tons of fish. The area is now a state park.

Can a concrete ship be used as a mine sweeper or for some other strategic use case?