The way I see it, posts set into concrete never rot 'In' the concrete, it's always at the surface where the rot starts,

where there's a Food Source, Moisture, and Oxygen

.

So, you set your posts into a concrete footing, making sure the top part of the footing is sloped away from

the post, and above grade enough so that it stays above the damp. Surrounding area must drain well also.

Then, you wrap that vulnerable point with a copper band, which, as it oxidises,

releases a copper solution which kills all rot,  mold etc.