I mean, unless they’re directly cutting up old buildings into the final block shape for this (which would be a nightmare to actually do), it doesn’t actually help that much. You can’t practically un-make concrete and turn it back into that slurry that comes out of the mixer truck, AFAIK all “recycled” concrete means is old concrete gets crushed into fragments and used in place of gravel. But the gravel is not the truly problemic part, you still need more cement to bind those fragments into your desired shape, which releases carbon and consumes water.

(Reposted from another reply in the same thread)