Yes, I do worry a little about that. One TBN fix I have seen mentioned is putting a piece of PVC pipe on the bucket edge. That way the pipe rides on the asphalt and not the metal bucket edge. I have not tried that yet.
The snow melted today and my bucket scratches concrete and tears through the tar making light covered scratches, especially when back dragging. Blacktop can be sealed, but I'm not sure what the aesthetic fix is for concrete.
jmf