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Old 07-21-2009, 02:21 PM
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Default Concrete curing time

Hello,
I built my stand and poured the concrete hearth this past weekend. I covered the wet slab with burlap to keep it moist overnight and in the morning I found some of the portland cement had coated the surface of the concrete, maybe a total of a cup for the entire slab. I assume the burlap helped wick this. The slab seems solid but how do I tell? Also, how long should I let it cure before I start with the insulating layer of portland and perlite?
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Old 07-21-2009, 03:40 PM
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Default Re: Concrete curing time

Don't worry about the surface of your concrete slab. Concrete will cure underwater. How do you think they build bridges? As long as it's the right thickness and properly reinforced you are good to go. You can place your vermiculite concrete right away: at one point it was suggested to pour the support slab and the insulating layer one right after another. You should let your concrete cure for a week before proceeding with your floor and dome.
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Old 07-21-2009, 07:33 PM
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Default Re: Concrete curing time

I agree. Keep it wet for a week.
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Old 07-22-2009, 09:37 AM
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Default Re: Concrete curing time

You mean letting the portland and perlite mixture wet cure for a week? Thanks
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Old 07-22-2009, 10:03 AM
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Default Re: Concrete curing time

I would: it takes a while to solidify into the cork-like consistency you're looking
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Old 07-22-2009, 10:24 AM
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Default Re: Concrete curing time

Quote:
Originally Posted by dmun View Post
I would: it takes a while to solidify into the cork-like consistency you're looking
Okay, that's good. One more question: The 5 parts Perlite to 1 part Portland Cement, that's by volume correct? Once poured do I just screed the mixture level or should I try and float it flat like the concrete?

Thanks
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Old 07-22-2009, 03:44 PM
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Default Re: Concrete curing time

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The 5 parts Perlite to 1 part Portland Cement, that's by volume correct? Once poured do I just screed the mixture level or should I try and float it flat like the concrete?
Yes, by volume, mix the dry ingredients until fully coated then add water until just wet.

You won't be able to float this mixture, the best you're going to be able to do is pat it flat on top with your trowel.
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Old 07-23-2009, 03:39 AM
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Default Re: Concrete curing time

Quote:
I found some of the portland cement had coated the surface of the concrete
This is typically something you will experience if your concrete is on the wet side. In serious cases it could weaken the concrete due to depletion of cement, but for such small structures and dimensions we are talking about here there is nothing to worry about.

regards from Karl
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Old 07-28-2009, 01:59 PM
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Default Re: Concrete curing time

Thanks for all the answers
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