Unusual problems with concrete not curing properly


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Old 03-07-12, 08:33 PM
G
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Unusual problems with concrete not curing properly

I've been in the residential construction industry for many years, and just when you think you've seen it all, something comes up that throws you!!! Simple stuff...so I thought. Small bathroom floor..approx 4'X4.5'. After demoing the tiled floor, we poured concrete with fairly large aggregate. No problems! A few days later we poured a self leveling mix...no problem. The next day, we poured another inch or so of the same mix ....This time, not the next day but the day after that, I walked into the bathroom to be met with a large hump in the middle of the floor. What happened, it seemed, the self leveling mix developed a large air pocket between itself, and the previous days pour. What seemed really odd is the fact that it seemed to not have adhered at all to the prior days pour because it came up so cleanly, without damaging or even affecting the layer underneath. Well, we had some concrete left, so I used concrete in place of the self leveling mix. BUT!!!! AGAIN!!! After the first concrete pour, I had made another pour the day after that. O.K., not the next day but again, the second day after the last pour, I hear a crunch as I step into the bathroom....and again, a hump in the middle of the floor...not quite as large as the self leveling mix, but nevertheless, what seemed to be air pockets developed between the second pour and the one before that one! Can anyone explain this? Any insight would be greatly appreciated. I don't think I've ever come across this type of situation in my life.
G P Richards
 
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Old 03-07-12, 08:45 PM
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Sounds like one of the ingredients of your self-leveling mix is undergoing some form of chemical reaction, resulting in outgassing. Either with one of the components of the previous layer or with a bonding agent that may have been used between layers.
 
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Old 03-08-12, 10:40 AM
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Most self levellers that I've seen require that the underlying concrete be cured before they can be applied. You say "after a few days" you put on a self leveller. The concrete you poured would need to cure for 28 days prior to applying a topping. I'd guess that's the problem (even if you've done it before with no problems). Read your product's literature to find out what they require.
Out of curiosity, what self levelling product did you use?
 
 

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