Since it is for the english language area, I am not sure. I was speaking for the german one. Maybe an british opionion would be nice. Honestly, I forgot, you can accomodate it to something useful. (However, remeber this good is available from 1919.)
Okay, after a little bit of search-engine-fu, I realize I was mistaken about what was actually being produced. I was picturing small stones. It appear to be referring to what we in the States call "cinder blocks" or "concrete blocks" (though some of the pictures I found were not of cellular blocks but columns, arches, and other forms. Shipping cinder blocks by rail would make a lot of sense, as would selling them at a construction/home market.
I wonder how difficult it would be to make the factory produce cinder blocks at first, then both cinder blocks and bags of concrete mix when mix bags became available historically.
My recommendation, as an English speaker, would be to call the good type "Concrete Blocks" and the factory "Concrete Factory" or "Block Factory".
I don't want to make these changes without hearing from one or more British or European native English speaker.
This type of factory could make other things from similar inputs, including "bricks", "pavers", and "birdbaths".