bill allemann wrote:
I need to install a treated 4X4 as a gate post through a slab (yet to be
poured).
I can't surface install on one of those galv brackets, because the 4X4 needs
to support
a gate and small fence section.
Would the 4X4 last better if cast right into concrete, or should I make a
well for it, filled with compacted aggregate?
The bottom of an aggregate well can connect to grade for drainage.

Just spend a couple extra bucks and make that one 4x4 a .60 pcf (or .80
pcf if you can find it). Paint the bottom with some tar or creosote,
and make sure to put a cap on the top. Go ahead and sink it right into
the concrete. Slope the concrete slightly away from the post. It'll
last forever.