Steve B wrote:

I want to pour some Sonotube bases for a metal awning and use the
weight of it to hold down the 3" x 3" x .120" posts.

You mean the posts are 10-feet long, right?

You can get 3"x3" posts that are 10-feet long?

Sonotobes will be about 24" diameter, and 18" high, maybe a little
more so they can be used as places for pots, or to sit on.
I intend to look up the mix in my Pocket Ref, and just do it by
counting shovels of each, and gallons of water, or just look at
it for the right consistency.

I don't know if sonotubes are made larger than 12" diameter. If they
are, I've never seen them at home depot.

If your tube is going to be sitting directly on flat ground, what are
you going to do for the bottom of the pier? How are you going to insure
that your concrete won't leak out the bottom or that the tube won't rise
up, leaving you with a big concrete pancake?

Do you think I can do enough mixers of it to have a monolithic
pour before setting time comes? I'd say three to four mixers
full per pier.

Each pier would have a volume of 4.7 cubic feet assuming 18" high and
would weigh 680 lbs.

This is exactly the mixer I have:

http://www.hometips.com/articleimage...r_electric.gif

I can mix about 175 lbs worth of concrete (about 1.2 cubic feet) per
batch. So with a mixer like that, it would take you 4 batches to fill
one of your piers.

I've been using my mixer to make a concrete sound wall that has sections
3.5 inches wide, 4 feet tall and 10 feet wide. It takes about 9.5
batches to make each section. It takes me about 15 to 18 minutes to mix
and place each batch, or about 3 hours in total. I use a vibrator after
batch 4, 8, 9 and 10, and I can tell that the first batch is setting
when I vibrate after batch 8.

So basically I can mix and place about 10 cubic feet with a relatively
small mixer in about 3 hours and maintain the concrete as a single
monolithic slab. You should be able to easily do the same with only 4
batches - or less if your mixer is larger than mine.

I probably wouldn't set the posts in concrete for the awning. I would
connect the posts across the top with 2x4's, maybe put some diagonals in
as well. The weight of all that wood plus the awning would be enough to
keep it down. Maybe drive a rod or long bolt into the ground at each
post to use as a tie-down. For more stability and weight, I'd probably
use 4" posts, maybe even 6" (which is actually 5.5").