I stumbled onto this article while working on a photobash of a solarpunk scene. I think it does a good job of explaining the concept but there seems to be something wrong with its certificates, which might throw an error in your web browser. https://nwedible.com/urbanite-broken-concrete-retaining-wall-as-a-garden-feature/
Just in case you don't want to check the link I'm also going to plagiarize a few quotes and images from the article:
"The marketing term for “old chunks of broken up concrete” is urbanite. Urbanite has a lot going for it: it’s durable and heavy like natural stone, reusing this product in garden and landscape design takes it out of the waste stream, it’s often a uniform thickness which makes it easy to stack or lay as a permeable patio surface, it’s often available in most urban locations, and it’s frequently free for the hauling. Free is good.
Drawbacks to urbanite can include potential contamination – this is more of an concern if your urbanite comes from a torn out commercial parking lot where all manner of auto fluids may have seeped into it than from the neighbor’s pool deck tear-out. Concrete itself can contain additives that might pose a health or contamination risk, although my feeling is that old, weathered concrete has probably already leached the worst of itself out somewhere else.
I probably wouldn’t use urbanite to build edible garden beds, but I can see great potential for turning this waste product in retaining walls, steps, and patio areas."
And a few examples of recycled concrete patios:
This last one came from https://www.terranovalandscaping.com/90/, which has a few other examples, including raised beds, so perhaps they knew their source of concrete was clean, or weren't worried about the potential for contanimation?
