In short: you can't use aluminium to reinforce concrete. You shouldn't even embed uncoated aluminium in concrete.
Quoting Corrosion of Non Ferrous Metals in Contact with Concrete, "Aluminium suffers attack when embedded in concrete". Corrosion of aluminium embedded in concrete causes total destruction of aluminium bars, therefore it's dangerous and inadvisable to use aluminium as rebar.
I don't have the reference at hand (I think it was in this book) but I remember having read about some accident caused by use of aluminium as rebar during a shortage of steel caused by some strikes in the USA. Aluminium bars examined after accident had completely disintegrated leaving just some white powder.
Update: I got the book again. My memory stated above is inexact, although the conclusion doesn't change. The book is Feld, Jacob. "Lessons from Failures of Concrete Structures". American Concrete Institute. Detroit 1964.
According to it, during the steel strike in 1959 several buildings in New York substituted aluminium conduit for the conventional steel item. It resulted in distress with cracking ceilings along the conduits due to aluminium conduits expansively disintegrating into white powder.
As you can see, the reference was about aluminium conduits instead of aluminium rebar. However, aluminium rebar in concrete would result in the same effects: disintegrating bars, therefore losing all strength and breaking concrete due to expansion.