epoxy = stronger than concrete.
atleast west systems is.
in the west newsletter a couple years ago they did tests in putting bolts into reinforced concrete using west....
the holes were oversized and either smooth or rough.
poured concrete into the holes.... bolt rips out easy
epoxy into smooth hole... bolt and epoxy plug rips out
epoxy into rough hole.... bolt epoxy and a fairly large chunk of the surrounding concrete rips out.