I am building a 30 by 50 ft steelbuilding. The stem wall/footers are built from 10 inch core BB ICF. I plan on pouring concrete directly from the chute, rather than renting a pump. The terrain is flat, so access  for the concrete truck is ok. Any suggestions or concerns?

Poured a full foundation out of a chute last year,[not my choice]. The treme is usually 8" which lets a lot of concrete fall so we used a couple of furring strips and 2 vise grips to restrict the flow and it worked reasonably well.

I'd have a vibrator on hand if you can just in case your slump is too dry. The end of a sawzall without a blade in it work pretty good too.

Not my first choice, but we built a V box out of plywood and 2x4 about 4 feet long with about 10 inch side walls that we could pull along the top of the wall to control the concrete flow, as well as keep the top of wall nice and clean. Pumping is faster, cleaner, and neat but the box did work and saved us on the pump cost for the at grade pour. As Smartwall has mentioned, pinching off the flow down the chute also helps - we did that as well. Good luck with it.

Thanks for all the input, specially the restriction of the flow from the chute. I will have a vibrator on hand with a 1" head. I cannot use the sliding box idea, as I have rebar sticking out of the top. Thanks again for all the advice,i will provide an update on how it went.

I've poured out of the chute with no problem. 10" is a pretty big target.

I suggest to use pump.
It is actually not so expensive.
I paid $1300 for 6 hours today.
You have to make at least 2 turns for 8 feet walls (4+4).
It will be a dirty job.
I guess you have a good driver.
If you have a success, It will be fun without pump.
Good luck.

It is actually not so expensive.
I paid $1300 for 6 hours today.

That sounds expensive to me! He said he's just pouring stem walls, so he's probably not going more than waist high.

Once you have place concrete in an ICF wall with a pump, you will never go back to a chute again...I don't even own a wheelbarrow any more.

Chances are for a stem wall, using a pump you will incur the minimum charge, usually 4 hours including travel, figure $ 650-800 depending on local pump rates