I think several of the posters might be misunderstanding the use of
concrete.
Concrete should be used as a footer pad not as a surround. You pour the
concrete Pad (Using Sono Tubes or such enhances the experience) and put an
anchor in the curing concrete. The anchor holds the post several fractions
above the concrete allowing for drainage.
The biggest advantage of using the anchor is that if the post does happen to
rot out, or you wish to enlarge the deck, the post can be removed and
replaced.
For those who live in high wind zones wind will lift up your deck if it has
not been anchored properly. Some codes require the Anchor method because
theoretically and deck could be pulled right out of the ground.
If you choose to put the post in the ground beware. PT is not always 100%
bug proof. It can make a fast channel to your house.
Several of you did address drainage with stone etc. However gravel can move
with leverage of a rocking post.

YC

The biggest advantage of using the anchor is that if the post does happen to
rot out, or you wish to enlarge the deck, the post can be removed and
replaced.
"Sean" wrote in message
...
Does anyone know much about PTT ?

If you dig a hole, put in some hardcore/gravel and plonk in a PTT ... back
filling with more gravel and compacting ... how will it fair with the
elements?

Basically, is it really necessary to concrete the posts in as they will be
securely held in place by the (above ground structure).