Newshound wrote:
I think you are all worrying about nothing. There's a recommended minimum
depth below the surface and once you are there very little happens because
the concrete will stay alkaline for a long time. Even sub-sea structures
like pier columns last a long time with mild steel rebar.

This thread is the first time I have ever heard of the steel needing to
be rust free. Iron left in sea water aggregates a lime scale concretion
that preserves it.

I would imagine that if rust was a problem the various agencies in
charge of the safety of building would put a stop to it and that the
concrete mufacturers would have invented an additive to safeguard
against the problem.

I imagine the problem with expanded steel is that the plaster or
whatever it is used with, does not completely immerse the metal.