Can I obtain a different density of a recycled elemental material?
I think it is risky. The density observed lower than the expected density of pure Al is indicative for the presence of something of even lower density than Al itself.

Similar in appearance to aluminium (density $\pu{2.7 g/cm^3}$, melting point $\pu{660 ^\circ{}C}$, source) is magnesium (density $\pu{1.7 g/cm^3}$, melting point $\pu{650 ^\circ{}C}$, source).  Both are used, pure as well as in mixture of other metals (alloys), widely.  Even to the point that they are mixed to form alloys with each other, for example in the frames of laptops 



(source)

or items that are used near the sea / in contact with sea water (source).