Slabs on Grade
Slabs on Grade
(OP)
I am sure that this has been discussed before, but how many of you put WWR in a slab on grade, and if so, do you follow the min. steel for temp. and shrinkage, or just a number for crack control.
Also, how many require a vapor barrier/retarder?
Also, how many require a vapor barrier/retarder?






RE: Slabs on Grade
Check out these threads. The subject has been discussed fairly fequently.
thread507-187489: Shrinkage, WWM & Synthetic fibres
thread507-144777: WWF vs Rebar: WWF vs Rebar
thread507-126594: Support of wwf in slab on grade: Support of wwf in slab on grade
thread592-152445: Slab on grade-no reinforcing: Slab on grade-no reinforcing
RE: Slabs on Grade
The use of vapor barrier/retarder depends on the situation.
If mositure vapor penatration through the slab would be a problem for a floor finish (carpet, tile, wood flooring, etc) or otherwise be objectionable, the I would definately use a vapor barrier.
If moisture penatration would not be objectionable (machine shop, warehouse, etc) then I would consider leaving it out.
When I do use a vapor barrier. I specify a fairly hefty one. I usually spec around the 15 Mil thick STEGO product. Tends to resisting tearing and getting holes punched in it prior to the slab being placed a lot better than thinner products.
JMHO
RE: Slabs on Grade
RE: Slabs on Grade
Around here SOG would typically have WWF supported on chairs to ensure it remains where it should when pourung the concrete.
RE: Slabs on Grade
It is quite impossible for concrete workers to place concrete on ground without walking on their work. Even with WWF pickers, they do not really know how far they are picking up the WWF and they are invariably inconsistent in their efforts. Consequently, the effort is wasted.
Contractor's hate rebar for slab reinforcement because it is more labor intensive and they have to support it off the ground, tie the bars, lap the bars, and walk inbetween or on top of the mat. They trip on it, etc.
But I force them to do it because I will never specify WWF ever again.
RE: Slabs on Grade
The only way that I have ever seen WWF wind up approximately where you need it is to pour the lower 2/3 of the slab thickness and then have a crew "walk the WWF in", set it on the freshly poured concrete and then pour the remaining 1/3. Even though the guys will step on it and push it down at various locations with their boots, the majority will remain in the upper part of the slab. (It is just the opposite of guys trying to hook it up.)Contractors, obviously, do not like this method as it increases their labor costs.
RE: Slabs on Grade
you are obviously not specifying enough chairs. Specify plastic chairs and more of them. Plastic chairs arent as likely to sink down as metal chairs.
csd
RE: Slabs on Grade