Time to Cure the concrete.

[asudavew]

Ok, I spoke with my father last night about the cure time on my hearth.

Now I've poured lots of concrete before but never anything suspended. All my past pours were on the ground.

So I asked my dad when I could take the forms off. He said, "Do you want the rules from the book?" I said, "Sure." He said, "One month." I said, "How bout in the real world?" He said, "One month."

That's what they used to do during commercial construction. He used to pour and build at the local Air Force military base. Strict government restrictions. They even had to do a slump test on each concrete truck to make sure the concrete wasn't to wet. He also helped to pour concrete and build the local state university dorm facilities and some of the buildings. Same rules there - wait one month before removing forms on suspended slabs.

My understanding is that concrete reaches about 80% of it's final strength after 7 days.

So I what I want to know is how long did everyone here wait before removing their forms from the heath.

[RTflorida]

1 week..(7 days)

[asudavew]

Originally Posted by RTflorida

1 week..(7 days)

That is what I was thinking.

So did you have any problems?

[Mojoe]

Pulled forms at 3 days, wet cured for 7, started to build on the 8th day. The Army Corps of Engineers are about as strict as the come. The one month ruling is what's known as 28 day strength and is a baseline for most commerical concrete work.

[asudavew]

Originally Posted by Mojoe

Pulled forms at 3 days, wet cured for 7, started to build on the 8th day. The Army Corps of Engineers are about as strict as the come. The one month ruling is what's known as 28 day strength and is a baseline for most commerical concrete work.

thank you

I will have no fears this weekend.

well maybe a few.....

[Ken524]

For mine (with a cantilever like yours), I pulled the forms after 4 days then kept it wet and covered for another 4-5 days. Hasn't collapsed yet

[Unofornaio]

We pull the forms later the same day on some stuff, stairs, porches anything that needs to be faced, curb an gutter... . Having the mix set up is not to be confused with at strength or even strong for that matter, the concrete is still VERY susceptible to cracking (in the span) and chipping. Use caution near the cantilever and all the edges, even a dropped brick hammer could take the whole corner off.

Remember this slab is going to experience expansion and contraction from the heat of the oven. A hairline crack that normally would not be an issue in a different application gets amplified each time the slab heats and cools.
I would leave the bottom hearth form till it has to come out, no rush there the other forms can come off the next day but why?. The cantilever should also stay on for at least a week if not longer especially if it may be susceptible to an accidental load even someone leaning on it could create an external or worse internal crack.

Here is my thing on the forms EVERYBODY is fired up to take the forms off right away..why? they are not in the way most of the time you don't need the wood for the next step. With the forms on you have the freedom to work on the brickwork without having to worry about the edges breaking off when you get on the slab or being chipped when you drop a brick or whatever.

[asudavew]

Originally Posted by Unofornaio

Here is my thing on the forms EVERYBODY is fired up to take the forms off right away..why? they are not in the way most of the time you don't need the wood for the next step. With the forms on you have the freedom to work on the brickwork without having to worry about the edges breaking off when you get on the slab or being chipped when you drop a brick or whatever.

Because we want to peak!



I went ahead and removed the side forms but left forms under the hearth, and support legs under the cantilever.

I guess we were thinking the same way.

[Unofornaio]

I know, I know. I hope that didn't sound like I was too peeved. Its just this forms coming off is another recent phenomenon created by the "home shows" that has customers that CLEARLY HAVE NO IDEA what they are talking about asking me "so when are you going to pull the forms?" in an almost concerned tone...the first few times I thought, what is up with this? I've been doing this stuff for YEARS and I have never had a customer ask me when are you going to pull the forms. Then another one and another and another its unbelievable how many ask now. Was there some "concrete special on dateline that I missed or something? ---HOme Shows are EVIL---

Anyway I know these ovens are a personal creation and everyone is anxious to see how they did. All I'm saying is, it is what it is. If there are voids they will need to be patched but they too can wait, leaving the forms on a few more days is just one less thing you have to worry about as your concentrating on the brick work.

[Ken524]

Originally Posted by Unofornaio

"so when are you going to pull the forms?" in an almost concerned tone...the first few times I thought, what is up with this? I've been doing this stuff for YEARS and I have never had a customer ask me when are you going to pull the forms.

We had an in-ground pool installed this past summer. They did cantilever forms over the edges of the pool. Guess what I asked the "See-Ment" guys after they were done?

Guilty as charged

Cordially,
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