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Old 06-29-2008, 10:05 PM   #1
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Curing concrete?


So we'll be pouring the 4x10x8" slab tomorrow and now I am reading about curing concrete. Is this something our concrete supplier will talk to us about or will they assume that we know what we're doing?

Well, we don't so I need enlightenment on how to cure this slab.

Something to consider, where the slab is located, there is no access to running water...

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Old 06-29-2008, 10:49 PM   #2
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Curing concrete?


haul water to it and wet with a garden can

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Old 06-29-2008, 10:52 PM   #3
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Curing concrete?


The concrete will cure whether you help it along or not. What you don't want to do is let the surface flash cure by having the wind blowing over it. Concrete cures by a chemical process called hydration, not by evaporation of the water. The water is used in the hydration, which is a chemical process. If your concrete's water is allowed to evaporate from the surface, it'll be ugly and potentially problematic.

Your concrete supplier will sell curing agent that you spray on finished concrete with a tank sprayer. This is pretty much a must. There are oil-based ones and organic ones such as soybean oil. I like bean oil personally, but it isn't available everywhere. After finishing, you coat the surface with the curing agent. Curing agent works pretty well as form release as well.

If you don't use curing agent (bad idea), you definately need to cover the slab to keep the air off the surface for a day or so. 6 mil poly will work.

Your concrete will set up fairly quickly, but will continue to really gain strength over the next several weeks. You will be able to walk on it and strip the forms the day after pouring (sooner in most cases, but why risk it).
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Old 06-29-2008, 10:55 PM   #4
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Curing concrete?


I would NOT recommend spraying it with water. Water will mix with the cement and create a slurry on the top surface, which is inherently weak. More water equals diluted portland, which means low strength.

I see this happen all the time. People over-work the surface, get too much slurry on top, and then add insult to injury by spraying the whole thing with water. Next thing you know you get a lot of evaporation, and the whole mess results in tiny surface cracks, spalling, etc.

Get some curing agent. They can bring it from the batch plant, and you can have a tank sprayer ready.
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Old 06-29-2008, 10:56 PM   #5
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Curing concrete?


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Originally Posted by thekctermite View Post
The concrete will cure whether you help it along or not. What you don't want to do is let the surface flash cure by having the wind blowing over it. Concrete cures by a chemical process called hydration, not by evaporation of the water. The water is used in the hydration, which is a chemical process. If your concrete's water is allowed to evaporate from the surface, it'll be ugly and potentially problematic.

Your concrete supplier will sell curing agent that you spray on finished concrete with a tank sprayer. This is pretty much a must. There are oil-based ones and organic ones such as soybean oil. I like bean oil personally, but it isn't available everywhere. After finishing, you coat the surface with the curing agent. Curing agent works pretty well as form release as well.

If you don't use curing agent (bad idea), you definately need to cover the slab to keep the air off the surface for a day or so. 6 mil poly will work.

Your concrete will set up fairly quickly, but will continue to really gain strength over the next several weeks. You will be able to walk on it and strip the forms the day after pouring (sooner in most cases, but why risk it).
what you are talking about is called Cure & Seal,,,,,,,correct ??
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Old 06-29-2008, 10:59 PM   #6
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Curing concrete?


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what you are talking about is called Cure & Seal,,,,,,,correct ??
I've always known it as curing agent or curing compound. Honestly, whenever I've used it or seen it used, it is in a white 5 gallon can with a concrete truck on it, but no brand name or anything on it. I am at concrete pours almost daily, and everyone gets the same "generic" stuff and just calls it "cure".

I've used soybean oil with great success, but it stinks like the dickens.
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Old 06-29-2008, 11:08 PM   #7
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Curing concrete?


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I've always known it as curing agent or curing compound. Honestly, whenever I've used it or seen it used, it is in a white 5 gallon can with a concrete truck on it, but no brand name or anything on it. I am at concrete pours almost daily, and everyone gets the same "generic" stuff and just calls it "cure".

I've used soybean oil with great success, but it stinks like the dickens.
did the cure say like 14%,, 18% ,,31% or anything like that ??
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Old 06-29-2008, 11:09 PM   #8
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Curing concrete?


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did the cure say like 14%,, 18% ,,31% or anything like that ??
Honestly never paid that much attention. You're leading somewhere....?
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Old 06-29-2008, 11:13 PM   #9
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Curing concrete?


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Honestly never paid that much attention. You're leading somewhere....?
we are probably talking about the same thing,,,i'd use that is it wasn't even going to need to be painted or epoxied ,,,and use the same later to seal as it wears off
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Old 06-29-2008, 11:22 PM   #10
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Curing concrete?


CS309 is the specification for curing compound, if whatever you use says that it complies with that you will be OK. If you are not going to do anything else with the slab, you can use a CS800 compliant cure and seal.
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Old 06-29-2008, 11:26 PM   #11
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Curing concrete?


Thanks for the responses.
Very helpful as always.

Will there be instructions on the container on how much to use per sq. foot of surface? Will one 5-gallon bucket be enough for our purposes?
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Old 06-29-2008, 11:30 PM   #12
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Curing concrete?


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CS309 is the specification for curing compound, if whatever you use says that it complies with that you will be OK. If you are not going to do anything else with the slab, you can use a CS800 compliant cure and seal.

We're going to install 3 cluster boxes on it (for mail delivery). It's about 600-700 lb total (including the weight of the shelter).
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Old 06-29-2008, 11:37 PM   #13
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Curing concrete?


5 gallons will be more than enough. A light coat on all the finished surface is fine...Just enough to coat, but not enough to pool all over the surface. A light spray is all you need.

Curing compound is not what gives the concrete its strength. The concrete develops all its strength on its own. What it does it helps keep the surface from getting screwed up from evaporation. The less air that gets to the surface, the better.
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Old 06-29-2008, 11:51 PM   #14
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Curing concrete?


Thanks!
You've been really helpful, thekctermite.
I really appreciate it.
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Old 06-30-2008, 05:06 AM   #15
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Curing concrete?


grump, for the size slab you're building, we'd just use a 2x4 to screed the surface, allow any bleedwater to accumulate on top, & give it a broom finish,,, if its really hot/sunny (above 90f), might cover w/plastic.

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