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]

Re: Time to Cure the concrete.

1 week..(7 days)

[asudavew]

Re: Time to Cure the concrete.

1 week..(7 days)

That is what I was thinking.

So did you have any problems?

[Mojoe]

Re: Time to Cure the concrete.

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]

Re: Time to Cure the concrete.

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]

Re: Time to Cure the concrete.

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]

Re: Time to Cure the concrete.

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]

Re: Time to Cure the concrete.

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]

Re: Time to Cure the concrete.

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]

Re: Time to Cure the concrete.

"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,
HGTV Addict

[asudavew]

Re: Time to Cure the concrete.

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,
HGTV Addict

Now that's funny!

[Archena]

Re: Time to Cure the concrete.

I like home improvement shows (there's one of us in every crowd, I know) but I can't ever remember seeing one where they were going ape - or even really concerned about - pulling the forms off. ~shrug~ Personally, I wouldn't have pulled them off until absolutely necessary anyway - there's no rush, why not give it the extra time? My Dad didn't pull the forms off our porch slab for six months - since it was getting too cold to work he just left them until work could resume.


Come to think about it, there was one episode of Monster House where they were nervous about getting the forms off. They'd had to demo a slab that was a foot thick (why the heck would you pour that much concrete for a patio slab?) and had been there for 40+ years so it took a lot longer than expected so the pour was delayed. But their concern was because they had to have everything done in five days - maybe having construction workers competing on a TV show isn't the best way to get work done?

[RTflorida]

Re: Time to Cure the concrete.

The how to shows can be a good source for ideas, especially for those without much DIY experience who are looking to branch out. Problem - many people don't apply common sense after watching and forget.....this is TV. As with every show, there is considerable editing and behind the scenes work going on that is never shown; we all know this, but many forget after getting caught up in the excitement of thinking - I can do that, or I want to do that.

As with anything that can disrupt or drastically change your lifestyle - or drain you bank account - Educate yourself. This forum being a great source (Again that common sense thing comes into play).
I certainly understand where Uno is coming from, seems the vast majority of people want everything fast and of course cheap. The modern, technological world has made be people believe that Rome or the modern equivelent can be built in a day.
And yes, I do watch HGTV, Discovery Home, Discovery,and TLC