Abandon formwork in place?

[mrengineer]

I am designing a structural promenade slab that spans about 20' between c.i.p. walls. Walls are about 20' high, and no need to put backfill in the dead space between the walls. No need for doors or openings into the dead space. Do you normally see formwork for this application abandoned in place?

 

[csd72]

They call it lost formwork where I come from.

Usually you can avoid it by using a composite metal deck and one line of timber shoring (which will be lost but is cheaper than a full set of formwork.)

Alternatively use soil as formwork, or leave a section of wall out until it is built so that the formwork can be removed.

 

[Taro]

You might also consider precast planks for the slab if they are available in your area and there is enough repetition to make it economical.

 

[graybeach]

Somehow I do not like the idea of such a large void left without access for inspection and maintenance. When we have this situation in bridge abutments, we generally include access doors and ventilation openings. One thought about leaving formwork in place. It does not seem like a good idea to do that with wood forms because the wood could rot, creating unpleasant gases.