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How are you addressing cracks?

#11
Yes, zip strips are magged into the crete then pulled afterwards. An easy joint.

Foam? Why would you fill it with foam? That's crazy. Put a tight hydraulic cement in the gap and seal it. You'll be fine.
JD Grafton
Concrete Answers for Flooring Problems
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#12
Foam? I want it sealed and not to worry about any filler pushing out. Besides I'd never adhere any floor ing to that slab. It's getting a floater.
Stephen Perrera dba
Top Floor Installation Co.
http://www.tucsonazflooring.com
http://www.floorsavior.com
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#13
My method of adressing cracks is:
1. Make sure they are dormant
2, Clean them out thoroughly all the way to the bottom, usually 1-inch
3, Use a high compressive strength patch about 7 -8,000 psi
4. don't over water the patch, instead dampen the crack with a damp rag.

Remember if the crack moves it will move.
Regards
Rayt
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#14
As for cracks being dormant.....

I mitigate slabs. I often don't see the slab until I get on the job site to begin work. Many of my slabs are young, less than 6 months old. They are still shrinking and moving, well they have over 90% RH or I probably wouldn't be there!

If a crack hasn't moved in a month, after I seal the slab it may very well move later! The slab has been drying out the top, the top has shrunk, and the slab is most likely curled a bit and raised at the control joints. When I epoxy that slab the moisture will redistribute and the slab will relax and un-curl a bit. If there is any patch in those control joints it will be squished out. I don't want my self-leveler in the joints and cracks because I am really going to rock the slab's world and it is going to probably change because of what I do.

That's how I see it from my view. Your mileage may vary.
JD Grafton
Concrete Answers for Flooring Problems
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#15
(08-26-2011, 02:30 PM)CC Solutions Wrote:  If a crack hasn't moved in a month, after I seal the slab it may very well move later! The slab has been drying out the top, the top has shrunk, and the slab is most likely curled a bit and raised at the control joints. When I epoxy that slab the moisture will redistribute and the slab will relax and un-curl a bit. If there is any patch in those control joints it will be squished out. I don't want my self-leveler in the joints and cracks because I am really going to rock the slab's world and it is going to probably change because of what I do.

"Fill it with cement, epoxy over it to seal it well, and put flooring on it. It will hold up"

So I am confused. You put cement in the crack not your self leveler then you epoxy over it / patch then put flooring on top. Seems like a contradiction.
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#16
A lot depends on what the moisture content is. If it is wet, above 75% it will tend to move as the slab goes into equalibrium.
Rayt
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#17
(08-31-2011, 11:53 AM)eaadams Wrote:  
(08-26-2011, 02:30 PM)CC Solutions Wrote:  If a crack hasn't moved in a month, after I seal the slab it may very well move later! The slab has been drying out the top, the top has shrunk, and the slab is most likely curled a bit and raised at the control joints. When I epoxy that slab the moisture will redistribute and the slab will relax and un-curl a bit. If there is any patch in those control joints it will be squished out. I don't want my self-leveler in the joints and cracks because I am really going to rock the slab's world and it is going to probably change because of what I do.

"Fill it with cement, epoxy over it to seal it well, and put flooring on it. It will hold up"

So I am confused. You put cement in the crack not your self leveler then you epoxy over it / patch then put flooring on top. Seems like a contradiction.

No contradiction! For a really large crack I'd fill it with a rapid setting concrete. For small cracks, I like to fill them with epoxy when I flood the floor, any that don't fill completely I fill with polyurea.

Concrete and self-leveler are two very different animals!!! You never want a patch or leveler in cracks. And you never mitigate over patch or levelers, your epoxy mitigation only goes on concrete.
JD Grafton
Concrete Answers for Flooring Problems
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#18
Another discussion beyond cracks is one of joints....

I read over some of the ardex moisture systems and for some joints they fill with a polyurea before system install, which I found interesting.

I guess a polyurea won't be as hard as an epoxy so it won't some day crack the slu on top and allow a moisture path through the system?

For active expansion joints it looks like they must be honored.
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#19
Some polyureas are HARD, while some epoxies are really soft. Don't let the name fool you.

Anything you use must be more flexible than the concrete and have some elongation properties so if the crack moves the filler stretches and doesn't crack. If the filler is too strong the moving concrete will still cause a crack, just in a new area that may be much worse than if it is kept on a nice straight control joint.

Keep in mind that no epoxy mitigation manufacturer will warrant the cracks. Some want a filler placed before the epoxy so the epoxy is continuous over the filler. Some want the crack filled with epoxy and if it has space remaining after the cure they call out filling the void with a flexible epoxy, polyurea, two-part urethane caulk or similar traffic bearing flexible repair.

Active joints are rare but yes, if they are designed to move you have to allow them to move.
JD Grafton
Concrete Answers for Flooring Problems
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#20
That is interesting. I have always been told that a joint filler should be crushable so that it will not pucker up with reverse curl when the moisture reequilibtates. See ACI 302.2 and the article http://www.google.com/m/url?client=ms-android-sprint-us&devlocsession=off&ei=31dxTujvB-b_sgfI8MupAg&gl=us&hl=en&q=http://www.silpro.com/education/Reverse_Curl_Article.pdf&source=android-launcher-search&ved=0CBYQFjAA&usg=AFQjCNFWXNBRlIEHEd-mkXHyIuwI8ckBkw
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