Humanity in my world has to deal with the invasion of inter-dimensional beings (Their tech level is around WW2 and in certain departments they're more advanced than we were around that period and in others a bit less).
Now things aren't going so swell. The invaders come in waves that are seemingly random, fortunately it seems to be random for the invaders as well meaning that whatever they're using to enter the world is not something they fully control either. (small portals and the occasional big portals appear often enough that they can supply their forces, but not the kind of mass portal spam you need for a massive armada to come through in a timely matter.)
Since my world has way more islands than ours the naval theater is quite important as most of the fighting is similar to what went on in the Pacific theater.
Anyway this whole thing has been going on for a while now and in certain places humanity isn't doing too good anymore. Child soldiers, encouraging the 'burdens' on society (cripples, chronically ill) to enlist in suicide units,... Dark stuff al around. The invaders also go on the extermination route so bloody are literally to the last man on both sides, which make battles extremely bloody affairs.
However supplies are important too and on certain places it is kind of getting difficult to get enough steel to make proper full steel warships, so those places are trying to build warships made out of concrete to compensate.
They've got experience with building concrete ships as many, many auxiliary vessels are already concrete ships and some shitty second line 'warships' nobody actually expects to do much of anything should they encounter an enemy. They're mostly just extra heavily armed merchantman running on coal or something else (gasification) as oil too is getting too expensive to waste on non-combat ships.
Anyway, my question is since as far as I know no actual warships were build out of concrete IRL and concrete is quite a different material than steel. What are the things one should keep in mind when building warships (ranging from destroyers to battleships and aircraft carriers) out of them?
Will they not be able to mount the same kind of caliber guns say the Nagato, Iowa and Yamato battleships could or would the material make them unusable for aircraft carriers? Would they be more durable or less in case of an attack?
In other words how does a ferrocrete warship hold up against a conventional steel one?
Like I said people of this world are in certain areas more advanced (in certain areas) then we were during the 40's, 50's and 60's though of course due to the nature of the war it's not always easy to swap supply lines to actually mass produce the new stuff.