ok, id heard of ideas for such things, and many of shore concrete fortifications called this, but this appears to be a real concrete ship, (not pikreate, concrete) i found this photo on the gwpda, any information on it will be appreceated
Concrete ships were certainly built and used in WW2 - as transports. The ultimate floating concrete stuructures were of course the Mulberry Harbours used to support the Normandy landings, parts of which can still be seen at the beaches today. So there is no reason why concrete ships might noy have been built in WW1
I have a memory of reading that in WW2 some concrete minesweepers were tried as they didn't set off magnetic mines thar easily. I think too that the Japanese were trying out the material because they just didn't have the steel for building coasters anymore.
I live just outside Houston (TX). There is a WWI concrete cargo ship scuttled in Galveston Bay just west of the ship channel and north of Pelican Island. It can still be seen from the ferry to Bolivar Peninsula. It was an experiment that didn't quite work out. All the topworks have rusted away, but the concrete hull is still there. You can see it on Google Earth if you zoom in close.