Questions about growing moss on concrete
So I am working on growing a moss garden in shady places of my lawn where grass doesn't want to grow. I'm a complete novice, though I'm enthusiastic. I've got patches here and there that I'm cultivating moderately successfully so far. I'd like to add some height differences to the area and so was thinking of incorporating some stones, preferably ones I can grow moss on as well, as inexpensive as possible.
I was thinking it might be fun and interesting to mix some concrete and make some abstract shape molds just by digging holes and filling them in with concrete, waiting for it to cure and then digging the concrete back up. Then flipping it flat side down and adding it to my moss garden, to grow moss on them.
I am wondering if anyone has done anything like this and if so, any tips or help would be appreciated. I also have this irritating feeling that in my reading up on mosses, I read somewhere about moss not growing well on some concrete, or something about curing it differently/longer before trying to grow moss on it, because the acidity/alkalinity of the concrete mattered. But I can't remember or find much about any of those things now that I want to, so I'm not sure what to do and don't want to waste my time and money on a shot in the dark. Any help or information would be greatly appreciated!