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Is there anybody out there ran in to the same thing that i have. I Would like to talk to them. I had a lot of problem with bad concrete; scaling, peeling,popping,lifting,cracking. I am so sick of redymix company telling me it is my fault. I been pouring concrete for 17 years i can't believe that i am doing something wrong. If you have an answers i would appreciate your info.
thank you
 

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Sounds to me as if it is curing too quickly. What is the average humidity in your area? Not that it really makes a difference. Where I am the humidity varies between 100-60%.
I was always taught to cover a new pour with VisQueen for at least 3-4 days. In the beginning, I thought it was for the rain. I found out later that it was for the cure.
Concrete cures by a chemical reaction. Water is a significant part of that reaction. If the water is allowed to evaporate before the reaction is complete you will have problems, such as internal stresses, which is what you are describing.
 

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Ask you're concrete company how much fly ash or silica fume they are using? Both of these additives are supposed to help the durability of concrete (and other benefits). But unless they use a midrange water reducer and plasticizer with it - it can dehydrate the slab rather quickly and it's typically a random process with finishing.
If you really want the perfect curing situation - flood the slab with water for 7 days. But who has 7 days? haha.
 

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I have had problems with overworking concrete. My Dad and I fuss too much, I believe. I have been told that as you work it over and over it draws more moisture to the top and this weakens the top of your work. I'm not sure if I buy that or not. The Romans cured their concrete underwater, did they have the same trouble? Hard to say. Have you changed your supplier recently? Have they changed theirs? If you haven't changed your technique, than something else has...Just my 2 cents
 

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Simon, you sure about that Roman thing? I've been to Italy and throughout Europe, a lot of their construction would be mighty hard to flood.
 

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Oops, what I meant to say is that they could (that is they had the know how) to cure underwater, not that they cured all of their work underwater. Heh. I didn't realize how silly that sounded until I read that over again. What is crazy to me is that for a few centuries, they had lost that technology. Thus during the Dark Ages, construction went back to stacking rocks and using mud to keep them together. Silly middievel builders, lincold logs are for kids.
 

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That section of history always defeated me as well. Humanity going backwards or standing still at best and much technology lost. I guess that is just another anology as to what the human animal can revert to in order to keep alive. You have to rember that as much as 2/3 of the population was lost to the plague during this time so much technology was lost.
The other part that astounds me is how long it took to get it back. Technically, massive construction wasn't resumed until Hitler.
 

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Yeah, strange about advances in technology. People are still confounded by the pyramids. That kind of massive construction is like 5000 years old (a heckuva lot more if you ask me...but who talks to historians anymore?). So 5k years ago they were building stuff that was the largest man made structure until the 20th century or so? What kind of wild aquatic apes are running this planet? And how come they tend to build things and lose the gumption, ambition, or know-how for a few centuries at a time? What, have we been shaking our collective etch-a-scetches ever few hundred years. I need answers here, I'm coming all to pieces! Heh.
 

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Some scientist believe that the earth has been capable of supporting life for most of it's own living cycle, almost 15 billion years, and that life has evolved and then been completely distroyed many times. our own cycle only goes bake 3.7 billion years. evolution/distruction, evolution/distruction, evolution/distruction.......The heart beat of God?

Sorry to make it worse Simon.

Just food for thought.

Bob
 

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Now we're talking HISTORY! I love it. I'm with you, Bob. Man's been building and wrecking this blue marble for a lot longer than the average archeologist thinks, you bet! There is a heart beat, brothers, and if you've almost taken the plunge off the second story roof and caught yourself just in time, I know you've felt it. Sa ha! The tool users rule, but only foor so long and then...start over. Man, what a way to stumble through evolution.
 
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Well I have been doing concrete for three years. ................. But I have three people on my team thats been on it for twenty five years....(lets just say IAm bless to have them....

We have poured over 150 jobs a year and not one have crack ( hairline yes but no major cracking)

The secreat i guess is to let the customer know to water the slab for three days.... I dont know why but It works. Know I live in Ca. So I dont know how this plays out in other parts of the country...


As far as the history.. It was my favorite subject
 
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I've built with concrete for many years and the BEST way to 'cure' it is to cover it with burlap and use soaker hoses to keep it damp/moist. In an ideal world you'ld keep it wet for 28 days (the amount of time it takes most concrete to cure) but if you do it for a week or so, you'll be much better off.
I've looked at things I've poured 20+ years ago and they still are holding up great. This is an old tried and true method, but nobody uses it much any more due to the time factor. Poly is the modern version - the point is keep it moist to cure - it's actually a chemical reaction using water as the catalyst.
 

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Bringing up too much water when trowling dillutes those fine cement particles in the concrete. You want more of the cement (not the water, gravel, sand) in the top layer for a stronger top surface. Also when you are covering the slab or wetting it you are preventing premature moisture loss from wind. The concrete has all the water it needs. It got that during mixing. It needs to cure without loosing that water so the chemical reaction can continue during the cure gaining strenght all along the way. If the concrete isn't cured the water evaporates and the reaction stops and you have a weak slab. (well...thats my take on it anyway)
 

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Hi cement Guy,
Popping is usually caused by soft agregate. Flaking and the other problems you mentioned are usually caused by surface water being driven into the cement. It is a timing thing. The surface needs to be fairly dry between finishing operations or excess moisture is driven into the surface which upsets the cement to water ratio and leaves a weak surface.

One product quality thing you can check yourself is with a slump cone. You can see if your supplier is putting in the minimum amount of cement or less with a simple test. Fill your slump cone, compacting as you go and once you pull the cone off to test the slump strike the side of the slump with your compacting rod with a good solid blow. If there is the minimum amount of cement in the mix, say 5 sacks the mix will slump even more. If there is less than 5 sacks in the mix and you strike the slump it will scatter all over.

There is an additonal problem you could be having with your supplier that they of course will not address. When they return from a job with some concrete left in the mixer less than honest suppliers add your batch into the old to save themselves a few bucks in material. You get a crumby job and they pass blame on to you. Over old concrete in the mix is very weak.
 

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hi

I had the same kind of problem when I made a new lid for my septic tank last summer, and in my own case, I believe a weak mix needing more portland, like hj said, was the cause. I would also say you will be just fine finishing it off with some thinset prior to tiling. Or, maybe something like Mapei's compatible "Planipatch" might be a little better if you have to fill 1/4" or more
 

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Is there anybody out there ran in to the same thing that i have. I Would like to talk to them. I had a lot of problem with bad concrete; scaling, peeling,popping,lifting,cracking. I am so sick of redymix company telling me it is my fault. I been pouring concrete for 17 years i can't believe that i am doing something wrong. If you have an answers i would appreciate your info.
thank you

More information needed. If you have been doing this for 17 years, and this is your occupation, I would find it incredible that you don't know what causes the conditions you are describing. If it has happened all at once, then the ad-mixes might have changed and you are overworking the slabs.
 
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