Closure Strips in Suspened Slab
Closure Strips in Suspened Slab
(OP)
I am interested in views on "closure strips" in suspended slabs. These are about 1 m wide strips left out of the suspended slab placements, for at least 28 days after the concrete is placed in tne floor each side of the closure strip, to allow some of the shrinkage to occur before the concrete is placed in the closure strip.
We figure that about 30% of the long term shrinkage will have occurred at 28 days after completion of the 7 day curing perod (i.e 35 days after placing the slab).
However contractos don't like the 28 day period and want to reduce it to 7 days, but at 7 days after the 7 day cure we figure that only perhaps 10% of the long term shrinkage will have occurred, which would not accomplish our goal of minimizing shrinkage cracking, This is particularly important where the slab soffit forms the finished ceiling of the apartments.
I am interested in knowing if closure strips as described above are generally being used?
If so, for how long do you keep them open?
Any other way that you are dealing with shrinkage, or do you just ignore it?
We figure that about 30% of the long term shrinkage will have occurred at 28 days after completion of the 7 day curing perod (i.e 35 days after placing the slab).
However contractos don't like the 28 day period and want to reduce it to 7 days, but at 7 days after the 7 day cure we figure that only perhaps 10% of the long term shrinkage will have occurred, which would not accomplish our goal of minimizing shrinkage cracking, This is particularly important where the slab soffit forms the finished ceiling of the apartments.
I am interested in knowing if closure strips as described above are generally being used?
If so, for how long do you keep them open?
Any other way that you are dealing with shrinkage, or do you just ignore it?






RE: Closure Strips in Suspened Slab
Maybe ask the contractor if they will take the liability if they pour sooner and there any problems.
RE: Closure Strips in Suspened Slab
I have not used, but some times shrinkage compensating concrete may also be specified.
Do we ignore it? Absolutely not. It has to be catered for, either in the design or through good construction practices.
RE: Closure Strips in Suspened Slab
Dik
RE: Closure Strips in Suspened Slab
RE: Closure Strips in Suspened Slab
So close them at the coldest time possible and you will be far better off. Coldest time of the day is normally late night, and coldest time of the year. So, if waiting 3 months pushes you to a 20C higher temperature you might be better off doing it earlier!
And get it done at the coldest time of the day!