Thank you, that helps clarify my thought process on the pour. My plan for the forms is to build a stud wall with 2x6's and 3/4 plywood on the inside of the wall to create the form. I will drill half inch holes into the concrete slab through the sill plate of the stud wall and pin it into place with half inch lengths or rebar. This will stop the forms from sliding or moving from the weight of the concrete. The studs will be 12 inches apart. I can go closer if you think that will help. Then I plan on building a L beam along the sides of the forms every two feet. Basically screwing in one 2x6x16 onto the studs on the flat side, then screwing another 2x6 onto that one on the edge. The L shape beam along the face of the stud wall will provide a huge amount of stiffness ans strength to the forms. It will also give me a solid mounting position for bracing that will go across the length of the room. The bracing will go from wall to wall, and in my mind, looking down on it, it will look like a checker board.
How thick were you planning for the bottom slab? And, how thick are you planning for the walls? If I were designing this, I would treat the walls as a retaining wall for design purposes. when I did this those many years ago, in CA hard adobe clay, not TX clay which I have no experience with, the design called for 12" thick walls and a 12" footer in an L shape. There was #4 (1/2") bar on 12" centers along the vertical walls. This was bent into an L shape and the other leg of the L was used in the footer. While it is certainly possible to finish the footer and use the top surface as a floor, there are going to be a lot of construction activities happening on that concrete, and it may be a better idea to build the footer and walls and plan on pouring a finish slab for the floor after that. The rebar was spaced 3" from the outside of the wall, and 3" from the bottom of the footer. This dimension is important for the strength of the final wall. Use dobes, or preferably rebar chairs.
In this design, I would make the entire floor the footer for the retaining walls...
When I poured the footer I used a tapered 2 x 4 to form a key to lock the vertical wall to the footer.
2 x 6 studs on 12" centers is very close to what I did and that part worked OK. I would not pin the forms the way you describe. The reason is that there will be tremendous force on the forms at the bottom and when the concrete cures the bottom 2 x 6 will be tightly compressed between the pins and the concrete wall. The only way to get it out will be in splinters, which will also damage the plywood. Instead use the rebar dowels to pin a 2 x 4 spacer just outside of the form. The spacer will have to come out in splinters, but the form will them come free and can be disassembled for re-use. Just to be safe I would pin this on 6" centers.
During the concrete pour, the forces on the forms are hydrostatic and will be much greater at the bottom than at the top of the form. If I were doing this, I would put the L-braces at 12", 24" 42" 60" and 84" for a 96" wall. Then I would pour in lifts. When you vibrate the concrete during the placement of each lift, be very careful not to liquefy the previous lift. Just the top inch or so of it.
Think out how you are going to handle the corners very carefully before you build the forms. The 2 x 6 studs are going to have to be carefully spaced to allow a leak-tight corner. And, I would place the L-braces so that the the horizontal parts can overlap in the corners. 3/4" higher than nominal on the North & South walls, 3/4" lower on the East & West. Drill a 3/4" hole through both and drop a 3/4" bolt through to hold them together.
This is going to require a lot of lumber just for the forms, but when I take down the forms, I will use them to frame up my addition. It will be 24ft by 48ft long with 12 foot walls. So I will cut every one of those 2x6x16's down to 140 5/8 inches for the studs of my walls. Then use the rest for blocking between the studs. I am going to cover the interior walls in 3/4 inch plywood, so that will also be reused
Are you going to run the 2 x 6 braces with the 6" side horizontal or vertical? I think you want them horizontal, and screw them together at each crossing. Also, block the different courses together to help prevent buckling. Crown them down, if you know what I mean. When they come under compression, the blocking will transfer the buckling forces to the footer. Staggering the L-braces as in the paragraph above will mean that the cross-braces go over-under exactly right.
Most of the forms I have used are coated with diesel fuel before the pour, which acts as a mold release. If I was going to re-use these as walls in a living space, I would look for something which had a more appealing odor than diesel fuel or even used motor oil. Any oil will work and I think non-detergent 30 weight might be easier to live with afterward. Even better, spray them with the liquid wax intended for kitchen floors a couple of days ahead of time. Just be sure to let it dry well.
Instead of hiring a pumper, I was thinking that I could have two cement trucks there at the same time, but at either corner. I didn't think about having them go slow and doing it in lifts. That makes sense, so I will probably have to pay a little extra to keep them on sight longer then they want to be just to keep them going slowly.
Don't have two trucks at once. Only having one will slow things down considerably. Also, space out when they arrive. It will be a longer day for you and your workers, but if those forms collapse, you are going to have a huge mess on your hands.
