Difficult Concrete Slab Pour
Difficult Concrete Slab Pour
(OP)
All,
We are building a new concrete arms vault inside an existing building. There are existing walls on the north and south side of the vault that we will be pouring up against. There is only about 7.5 inches from the bottom of the existing joist to the top of the new concrete vault roof slab. How do you foresee the contractor pouring the roof slab? Is it possible to pour the slab and set the steel reinforcing without removing the roof deck? Please see the attached drawings. Thanks in advance.
We are building a new concrete arms vault inside an existing building. There are existing walls on the north and south side of the vault that we will be pouring up against. There is only about 7.5 inches from the bottom of the existing joist to the top of the new concrete vault roof slab. How do you foresee the contractor pouring the roof slab? Is it possible to pour the slab and set the steel reinforcing without removing the roof deck? Please see the attached drawings. Thanks in advance.






RE: Difficult Concrete Slab Pour
It will likely be less costly and you'll get a better job if you remove the roof decking. Otherwise, you will not be able to check any of the concrete placement across the 15 feet each way. Further, getting the rebar in place and tied will be almost impossible without the deck removal.
RE: Difficult Concrete Slab Pour
The other thing of concern is the fluid concrete pressure against the existing walls.
RE: Difficult Concrete Slab Pour
RE: Difficult Concrete Slab Pour
RE: Difficult Concrete Slab Pour
RE: Difficult Concrete Slab Pour
A side question on designing fluid containing structures (or in this case checking the existing walls that they will be pouring against); does a fluid in a structure that is infinitely wide exert the same lateral pressure as a fluid in a structure that is only say one foot wide (infinitely skinny)? The height and density of the fluid being constant. Seems to me at some point the width should have an effect.
RE: Difficult Concrete Slab Pour
Typical practice for wall forms against existing walls, from what I see here, would be to Hilti some coil rod into the existing walls, add B1 coil ties or similar and attach a wood form on the open side of the new wall. The contractor will not want to pour this as a one sided form with the existing wall taking the full unbalanced pressure. The existing wall then only needs to be able to span between the embedded rods, which will be in something like a 2' by 2' grid. If you really need to, you can restrict pour rates and temperatures per the ACI concrete pressure equations to reduce the concrete pressure.
The roof slab is the more difficult item.
RE: Difficult Concrete Slab Pour
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RE: Difficult Concrete Slab Pour
RE: Difficult Concrete Slab Pour
RE: Difficult Concrete Slab Pour
RE: Difficult Concrete Slab Pour
RE: Difficult Concrete Slab Pour
RE: Difficult Concrete Slab Pour