How Should I Fill In a Hole in Slab Around Floor Drain
If the PVC drain indicates the age of the plumbing and the house, or at least when the slab was installed, there should be a layer of poly acting as a moisture barrier in between the concrete and gravel. Aside from that, all you need is to add the original gravel back into the hole and repair the vapor barrier and finish off the fill with a bag or two of concrete from any local building supply, big box or otherwise. A detail that would be good to do is be sure the hole cut inti the concrete floor is not all undercut. As in, the concrete should not be broken out so the hole is larger the bottom edge of concrete than the concrete at the floor level. A little undercutting is ok, but the concrete you add needs to lock in so it will not settle down away from the original concrete.