In2art;
Concrete is one of my many responsibilities as a maintence worker for one of the local school districs here, and without asking you a ton of monotonous tech questions about the TYPE of quickcrete, or the average weather, i. e.; moisture, humidity and temperature, it would be safe to remove the forms after a few hours of setting.
However; the thickness of your pour dictates the time needed to truly set. Also the longer the set the stronger they get, and if you plan on moving them more than a few times, you may want to consider reinforcing them with wire or fiberglass mixed in. If your mix has aggregets ( rocks ) in it , okay, but, if it doesn't then care must be taken during their set time because if they dry too fast they'll crack, so you must either keep them moist on top or work them over with a finishing towel after about an hour, again depending on the type you have. It may seem too hard but only for a while. If mixed right and worked back and forth, you'll be able to see the moisture come up, this is called the cream.
I've been thinking on doing something like that using cut sections of 5 gallon buckets and other circular forms of different sizes. something else you may want to think about is using polished or tumbled rock as an aggreget and after a couple hours run a steady stream of water over your pour while it is still in its form. I think you'd like the out come.
You can also pour only half and press in rocks to a desired pattern, just do a dry run first to make sure it all fits.
GOOD LUCK AND HAVE FUN!
