There are a few finishing touches to add to the formwork.
Firstly, all the mesh is supported along the exterior edges by some 8mm rod placed through holes in the formwork and held in place by a nail in the upper formwork supports. This stopped the edges of the reo from sagging.
Secondly, all the mesh chairs were cable tied to the reo. This mean that when we walk on the mesh, the chairs stay in place – very important. I put a chair every 3 grid positions. This is more chairs than you need, but it means that when you walk on the mesh, everything stays where it should and does not sag.
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Thirdly, I added a permanent screed bar along the middle of the slab. It is made from 50x50x3 angle iron, and supported by star posts driven through the plastic. These height of these posts were set by a string line and a dumpy. I cut a vertical slot in the top of each post for the angle iron to sit in, and a slot/rebate in the formwork. This proved to work really well. The screed bar gave us a 3m width to screed of against, except for where it passed the alcove.
Lastly, I had to place allthread rods that would be used to tie down the steel beam posts. I made a template of the rod positions, and made two boards (one for each side) that would sit in the concrete to hold the rods. The template would later be used to drill the steel base plates for the posts.
To stop the rods from pulling out of the concrete once the concrete was dry (concrete can shrink), I welded and angle iron foot onto each rod.
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Notes for next time:
All the reo was well tied together.
The all thread rods need to stick up out of the slab more. They can always be cut off later once the steel is bolted in. Buy extra rod if needs be – its better than them being too short once the grout is layed up and the steel plates are in place.
Brace the all thread rods diagonally in the slab with a bit of reo so they stay vertical. The timber plates they are held by can move a bit as the concrete goes in.