Our code for a slab foundation is 4″ of concrete supported by a 12″ wide by 24″ tall grade beam.  Every jobsite I’ve visited always has a first pour of about 8″-12″ deep (no forms, just into a trench with the proper rebar) with some rebar coming out.  Several days/week later, a second pour is pour is made making up the last of the below grade foundation and the slab for the floor.  This is formed in the traditional way. 

From L.A.’s Type V sheet, there is no reference on the rebar required to tie the first pour to the second.

I have read several hundred posts on this site and Taunton’s ‘Foundation and Concrete Work’ cover to cover.  I also looked at 50+ concrete books at our local builder’s bookstore.  Most/all of the narrative/photos show this first pour as this 6″-8″ inches thick and have a 2×4″ keyway for the stemwall to sit in.  But nothing I’ve seen describes how the remainder of the grade beam (and its rebar) plus the slab floor is tied together with that first pour. 

For a 24″ high grade beam, is it OK to have, let’s say, a 16″ beam pour on top of a 8″ pour?

How do you folks do it?

Thanks in advance.