Plain reinforced concrete is fine to repair and work with. Very basic: Erect temporary supports around the area if its load-bearing, saw-cut/hammer out the work

Plain reinforced concrete is fine to repair and work with. Very basic: Erect temporary supports around the area if its load-bearing, saw-cut/hammer out the working area, splice and retie any reinforcement, prepare the existing concrete surface for a fresh pour, pour and cure. Certainly more involved and time consuming than, say, replacing some siding or moving a wall inside a stick built house but its all doable. Pre/Post stressed components? Yeah good luck.