# Concrete cure time



## geigerr (Sep 28, 2012)

I am getting my patio extended with 4inch 4000 PSI concrete on gravel base layer with rebar that is pinned to the house. The job was suppose to be completed weeks ago but we gotten 3 weeks of rain. It looks like the slab will be poured Monday afternoon. I am planning on building a pre cut gazebo on it. It weighs 700lbs and I need to anchor it in. If I had the correct dimensions I would wet set the anchors but the company gave me a crap build diagram, and I would hate to be off. I’m planning on building the frame setting it in place than drilling a hole for the anchors. What would be adequate curing times for it to hold the weight and drill into?


----------



## de-nagorg (Feb 23, 2014)

Different times for different climates.

We do not know where your here is, so we won't guess.

I would have steel plates of about a square foot, embedded into the patio, placed at an approximate dimension of the expected size for the gazebo. 

This will give me something to anchor to, later, maybe a month later. 

Then wait and drill into the plates, and anchor to them .


ED


----------



## geigerr (Sep 28, 2012)

de-nagorg said:


> Different times for different climates.
> 
> We do not know where your here is, so we won't guess.
> 
> ...


Location would of been nice. I’m in KC area, and we are starting our summer. Temperature are 75 to 100 with a breeze. My back yard get complete sun with no shade from 12pm to 8pm.


----------



## Nealtw (Jun 22, 2017)




----------



## HenryMac (Sep 12, 2018)

The textbook answer is wait 28 days.

In your case, 

as long as you are just talking foot traffic and people erecting the gazebo, 
*and* you don't place anything that places point loads on the concrete (vehicles, machinery, etc), 
*and* the concrete was installed over a properly compacted aggregate base,
Then I'd personally wait a minimum of 1 week... you need that week to flood the concrete & insure it is properly hydrated.

If the concrete was just poured on top of the ground, wait 28 days.


----------



## geigerr (Sep 28, 2012)

HenryMac said:


> The textbook answer is wait 28 days.
> 
> In your case,
> 
> ...


That is what I was thinking, about a week. It has a proper compacted base. The drill holes will only be 1/4”. Im thinking about using epoxy and not wedge bolt either since I don’t want to wait 28 days.


----------



## geigerr (Sep 28, 2012)

Another question I got is which option would be the best for long term
Durability (photo attach). My old slab has a round corner. I am trying to determine do I just come straight off and make a round corner. Or do i have them pour a transition piece (circle). I think it will
Blend it better, but may just be weak in the corner. Thoughts?


----------



## geigerr (Sep 28, 2012)

geigerra said:


> Another question I got is which option would be the best for long term
> Durability (photo attach). My old slab has a round corner. I am trying to determine do I just come straight off and make a round corner. Or do i have them pour a transition piece (circle). I think it will
> Blend it better, but may just be weak in the corner. Thoughts?


I don’t think my photo posted. The transition area would be a 1’ x 1’ x 1’ triangle. It would be poured with the new slab & connected. Just worried it will crack.


----------



## HenryMac (Sep 12, 2018)

geigerra said:


> I don’t think my photo posted. The transition area would be a 1’ x 1’ x 1’ triangle. It would be poured with the new slab & connected. Just worried it will crack.


Yeah, that little transition piece will likely crack.

"_Reentrant corner cracks can ruin an otherwise impressive slab_"

https://www.concreteconstruction.ne...et-a-reentrant-corner-crack-ruin-your-image_o


----------



## de-nagorg (Feb 23, 2014)

How about placing some feature at that corner, like a large potted plant, firepit, table base, barbecue, or something else that you desire. 

To mask and cover the area, so the spot won't be seen, or have a lot of foot traffic on it. 

Unless you over pin it, it will be weak, due to it's size, and movement will occur seasonally.


ED


----------



## huesmann (Aug 18, 2011)

Concrete typically reaches 2/3 of its ultimate compressive strength after a week. That's probably enough to do you work on it, unless you're putting heavy equipment on it.


----------



## DIYERSCOTT (May 15, 2019)

Permit ? Footings ?


----------



## HenryMac (Sep 12, 2018)

DIYERSCOTT said:


> Permit ? Footings ?


Permits effect cure time? :biggrin2:


----------



## DIYERSCOTT (May 15, 2019)

HenryMac said:


> Permits effect cure time? :biggrin2:


Of course not, you should know that :bangin:

Cure time of concrete is relative, based on various factors involved in the mix, e.g., chemical additives, and the pour, e.g., weather.

The real question here is whether footers are required for the gazebo by the local building ordinances; hence, did OP get a permit for the job ?

If the local building code requires footers for a gazebo, they're required = permit and pre-pour inspection to make sure they are properly prepared (diameter, depth, etc.).

As an example, in Lenexa, a permit is required for most structures such as carports and gazebos.

Projects like this, if a permit is required but not obtained, are subject to rejection by the courts and/or insurance companies if such actions are needed at a later time.


----------



## geigerr (Sep 28, 2012)

DIYERSCOTT said:


> HenryMac said:
> 
> 
> > Permits effect cure time?
> ...


In my area a permit isn’t required if the structure is less than 200sq ft or I would of gotten one. Also, if the structure wasn’t prebuilt I would of wet set everything. They don’t have good dimensions available to be 100% correct of location. They said their footers are rated for 120mph. So unless a EF3 tornado hits my home I should be ok. Thanks for everyone’s input.


----------



## stadry (Jun 20, 2009)

*correct answer is no one knows when conc cures,,, however, we can measure time so conc's typically test'd at 24hrs, 7d, & 28d,,, test results're then compared to designed strength,,, after that, its thumbs up OR down
in REAL time, i'd personally give it a week of PROPER curing,,, then locate holes where needed & use lead drop-in's to anchor the gazebo,,, imo, much easier than pre-setting L-bolts & result in a cleaner-looking install*


----------



## Canarywood1 (May 5, 2012)

Concrete is typically tested at 7 -14- and 28 days, and is done in a laboratory that is equipped for it, the only time a job site would be tested after a pour is if the cylinder that was tested in the lab failed. Cylinders are typically made on the job site, and picked up the next day to cure under proper conditions until they are tested.


----------



## HenryMac (Sep 12, 2018)

As a visual for the OP...

When my slab was poured samples were taken and tested.

The first 3 photo's are applicable to onsite testing of air entrainment.

The 4th and 5th photos are of the 4 samples. They take an extra in case they need it due to a bad equipment failure or so they can verify results if the concrete tests under the required specification psi.

The 6th photo is a summary of the test results.


----------



## Canarywood1 (May 5, 2012)

A proper field test should include concrete temperature, slump, density, and air content, and should be submitted with the strength test report.


----------



## HenryMac (Sep 12, 2018)

Canarywood1 said:


> A proper field test should include concrete temperature, slump, density, and air content, and should be submitted with the strength test report.


I merely posted my summary of the 3 reports, not the report I received from the lab.


----------



## Canarywood1 (May 5, 2012)

Yes i understand that, my last post asked if they included that info in their report to you, i see they use the 4"x 8" cylinders, we use their big brothers 6"x 12".


----------



## stadry (Jun 20, 2009)

*henry, what were you placing,,, a bdge deck ? typically we only see that stuff on dot work +, occasionally, commercial/industrial/institutional (anywhere there's govt $$$*


----------



## Canarywood1 (May 5, 2012)

He had a floor poured in his new pole barn.


----------



## ktownskier (Aug 22, 2018)

de-nagorg said:


> We do not know where your here is, so we won't guess.
> 
> ED


This was to @geigerra,
Edit your profile and put in your location. If you want to put in your actual city, that would be great. Otherwise put in the nearest big city and state. 

For example, if you live in Duluth, GA. Don't put in Duluth as people might think you are in Duluth MN. Since, Duluth GA is a smaller community, you may want to put in Atlanta, GA. 

For me, I put in my city and Altitude, As it may make a difference in peoples response.

Just sayin...


----------



## stadry (Jun 20, 2009)

*odd, woody,,, i don't recall GaDOT tests at 14d - 24hrs, 7d, & 28d only,,, not saying it wasn't done,,, we never missed or had to retest,,, could be my memory too
i do recall 1 insp delaying placement of a 6'x12' patch which incl'd 2% CaCl while she conducted tests,,, she was extremely upset when i ignored her direction & dump'd it anyway*


----------



## bob22 (May 28, 2008)

Why pin the new slab?
My patio was pinned to house (insisted upon by inspector against the concrete guy's wishes). Now, at each pin location, the concrete patio has broken above the pin.I"m going to cut through the pin between slab and house walls and hope to just glue back what popped off. That or patch; neither is going to look great.
IMO, I wouldn't pin it but your mileage may vary.


----------



## stadry (Jun 20, 2009)

*what 'inspector' ??? idk of any specifier who'd pin to a structure - even loading docks,,, imo, your conc guy was 100% correct,,, fortunately the slab spalled instead of damaging the house*


----------



## Nealtw (Jun 22, 2017)

bob22 said:


> Why pin the new slab?
> My patio was pinned to house (insisted upon by inspector against the concrete guy's wishes). Now, at each pin location, the concrete patio has broken above the pin.I"m going to cut through the pin between slab and house walls and hope to just glue back what popped off. That or patch; neither is going to look great.
> IMO, I wouldn't pin it but your mileage may vary.


They have us do it here sometimes too, and when the dirt settles you have a bridge, It works but it has to be closer to the bottom of a 6 inch slab.


----------



## stadry (Jun 20, 2009)

*surprised, neal,,, even bridges aren't pinned to conc roadways*


----------



## bob22 (May 28, 2008)

stadry said:


> *what 'inspector' ??? idk of any specifier who'd pin to a structure - even loading docks,,, imo, your conc guy was 100% correct,,, fortunately the slab spalled instead of damaging the house*


Our town requires permits and inspections.


----------



## Tom153 (Nov 10, 2016)

For best outcome, mix should be about 6 sack cement/yard, as high a slump as you can stand for workability (usually you order high slump, but then the person overseeing the pour calls for more water only to improve the workability (experience matters here, since workability depends on, job site, temp, skill, size, shape...etc)). Pour during 70F - 90 F. After concrete sets, keep the surface continuously wet for at least 7 days, and up to 28 days to get max strength. (your contractor should take care of all this)

Since you intend to drill into the concrete and set anchors, near the edge of the slab, you will be inducing compression/tension into the slab, so you should let the slab cure a full 28 days, otherwise you risk cracking/spalling at the edge. Since your slab/gazebo will be around for many decades, a few more days dedicated to cure time is not significant.


----------



## geigerr (Sep 28, 2012)

Tom153 said:


> For best outcome, mix should be about 6 sack cement/yard, as high a slump as you can stand for workability (usually you order high slump, but then the person overseeing the pour calls for more water only to improve the workability (experience matters here, since workability depends on, job site, temp, skill, size, shape...etc)). Pour during 70F - 90 F. After concrete sets, keep the surface continuously wet for at least 7 days, and up to 28 days to get max strength. (your contractor should take care of all this)
> 
> Since you intend to drill into the concrete and set anchors, near the edge of the slab, you will be inducing compression/tension into the slab, so you should let the slab cure a full 28 days, otherwise you risk cracking/spalling at the edge. Since your slab/gazebo will be around for many decades, a few more days dedicated to cure time is not significant.


I agree the full 28 days makes the most sense. The slab just got pour and not please with the results. Good old KS weather cause issues with setting faster than expected causing a crappy top surface. They said they will resurface and warranty all work. Hopefully it doesn’t turn into a disaster.


----------



## HenryMac (Sep 12, 2018)

stadry said:


> *henry, what were you placing,,, a bdge deck ? typically we only see that stuff on dot work +, occasionally, commercial/industrial/institutional (anywhere there's govt $$$*





Canarywood1 said:


> He had a floor poured in his new pole barn.


Pole barn with a 10,000 lb capacity 2 post lift....

The thing is ... the testing was less than $200 and the dobies were $192. 

Spending $400 to ensure a $9,000 slab has a good base and reinforcing steel placed accurately seems to me to be money well spent.



Tom153 said:


> Since you intend to drill into the concrete and set anchors, near the edge of the slab, you will be inducing compression/tension into the slab


That's why epoxy anchors are awesome. They don't induce those high stresses you are discussing into the concrete. 

So the OP can start building his gazebo after a week. And the torque he applies to the nuts will be insignificant.


----------



## Canarywood1 (May 5, 2012)

stadry said:


> *odd, woody,,, i don't recall GaDOT tests at 14d - 24hrs, 7d, & 28d only,,, not saying it wasn't done,,, we never missed or had to retest,,, could be my memory too
> i do recall 1 insp delaying placement of a 6'x12' patch which incl'd 2% CaCl while she conducted tests,,, she was extremely upset when i ignored her direction & dump'd it anyway*





Sure, you got her panties in a knot when you dumped it after she told you not to.

We never had any 24 hr. breaks, just 7-14-28 unless specified otherwise.


----------



## DIYERSCOTT (May 15, 2019)

geigerra said:


> In my area a permit isn’t required if the structure is less than 200sq ft or I would of gotten one. Also, if the structure wasn’t prebuilt I would of wet set everything. They don’t have good dimensions available to be 100% correct of location. They said their footers are rated for 120mph. So unless a EF3 tornado hits my home I should be ok. Thanks for everyone’s input.


Not sure I agree with your police work there Lou...

The footings I'm referring to are the concrete footings; that is, it doesn't sound like you had footings added to the slab for the gazebo to sit on, because you didn't know exactly where the gazebo was going to sit (which also seems a bit odd to me). When you say "they" say their footings are rated for 120 mph, I'm thinking you're talking about the gazebo post bases.

Around here, concrete footers are required to be minimum 5,000 psi 12" dia. and 2' deep, and have to be inspected before the pour. That footer is then wet set in with appropriate fastener per post base manufacturer's requirements (8" j-bolt for example.)

So if you don't know exactly where the gazebo is going, it seems reasonable to think you did not pour concrete footers, and thus are going to rely on a 4,000 psi 4" thick slab, and something like RedHeads, to fasten post bases to slab.

Right ?


----------



## Nealtw (Jun 22, 2017)

stadry said:


> *surprised, neal,,, even bridges aren't pinned to conc roadways*


I didn't it is was a good idea. :biggrin2:


----------



## Canarywood1 (May 5, 2012)

Slabs should never be pinned to the foundation


----------



## Tom153 (Nov 10, 2016)

How about a picture. I'm curious what it looks like. Did they at least get it flat. That's the most important aspect for a floor/slab. Also curious what they intend to do to "resurface"; Hopefully they don't mean paint it.


----------



## geigerr (Sep 28, 2012)

Tom153 said:


> How about a picture. I'm curious what it looks like. Did they at least get it flat. That's the most important aspect for a floor/slab. Also curious what they intend to do to "resurface"; Hopefully they don't mean paint it.


It doesn’t let me post photos, there are waves in the slab and the texture isn’t consistent. I’m meeting with the company owner on Monday. I’m going to ask for the slab to be removed, and repoured by agreed third party. Seems like a good guy, but we will see what happens.


----------



## stadry (Jun 20, 2009)

*'Our town requires permits and inspections' - so what ? 
many areas/communities/localities/governments have the same - what they do NOT have are rqmnets that fly in the face of sound engineering/construction methods/mtls/practices*


----------



## stadry (Jun 20, 2009)

*


Canarywood1 said:



Sure, you got her panties in a knot when you dumped it after she told you not to. it wasn't 'her conc' til it pass'd testing - it was still MINE ! hot windy ga day, 2% ca cl in mix, & she wants to dawdle about testing slump/air,,, BULL**** ! 

had 12 hr breaks on this particular job - dot'd grab up samples & test every mix for air/slump,,, dot guys were great - never got in our way,,, end of day, we deliver'd samples to dot test lab &, while observed, put them into the wtr tank

Click to expand...

*


----------



## stadry (Jun 20, 2009)

*this thing's less than 200sf,,, 14' x 14' ? that's 2 guys here + others on wheelbarrows,,, 15/16' straight edge & a groover*


----------



## DIYERSCOTT (May 15, 2019)

geigerra said:


> It doesn’t let me post photos, there are waves in the slab and the texture isn’t consistent. I’m meeting with the company owner on Monday. I’m going to ask for the slab to be removed, and repoured by agreed third party. Seems like a good guy, but we will see what happens.


If tear out and re-pour, first figure out where the gazebo is going to go (can't be that hard right) and put in proper footings and wet set in proper fasteners.

It's rare that you get to fix your initial mistakes without unsubstantial penalty on your second go around.


----------



## DIYERSCOTT (May 15, 2019)

stadry said:


> *'Our town requires permits and inspections' - so what ?
> many areas/communities/localities/governments have the same - what they do NOT have are rqmnets that fly in the face of sound engineering/construction methods/mtls/practices*


So what ?

Professionals understand that local codes may vary from national codes and must be followed no matter what they, amateurs, think about them.


----------



## Tom153 (Nov 10, 2016)

Unless you can prove to them that the code is either not correct or not necessary for your particular situation. That would probably require a licensed professional report.


----------



## stadry (Jun 20, 2009)

*agree, scottie, yet i don't think ALL jobs in this town are blt according to local 'code',,, i'll bet when an inspector sees a professional stamp on drawings, he forgets/ignores his local codes & allows per plans,,, diy'ers are easier to bamboozle imo*


----------



## Tom153 (Nov 10, 2016)

Actually, sometimes they do. But if you are going to challenge them, you need to have correct analysis to prove it.


----------



## Tom153 (Nov 10, 2016)

That is true, if a contractor knows that a government inspector will be approving the installation, they will make sure it is within the code. I also know that some codes allow for professional judgement in meeting the code requirement. Most inspectors have experience of not only the code but "generally accepted construction methods".


----------



## stadry (Jun 20, 2009)

*maybe here's 1 reason,,, to admit the code's incorrect would incur a large liability to the 'town' - its easier to sweep that possibility under the rug with a wink*


----------



## Tom153 (Nov 10, 2016)

No. Codes do not verify that a design is safe nor "good". All the codes do is set a standard to meet, and inspections just verify that something is built to the code. Codes change over time, based on knowledge of construction materials, methods, and also failures. If an inspector finds a code that is not correct, they will do the work to change it to make it correct. Typically when a code is updated, work completed per past code requirement is "grandfathered". Sometimes, if that grandfathered work is ever changed, it might have to be "brought up to code".


----------



## Tom153 (Nov 10, 2016)

Most codes allow a design to be "out of code", if they are prepared by a licensed Professional Engineer. The reason is because the Licensed professional Engineer is taking personal responsibility for the design, which includes making sure that the project is completed per the design. Usually designs are well within the code requirements; but do not necessarily have to be. If the licensed professional engineer followed commonly accepted engineering design methods, then the design will be as safe as any "code requirement". By the way, the codes are just based on commonly accepted Engineering design requirements, and are generally prepared by licensed professional engineers, and generall the administration of those codes are overseen by licensed professional engineers.

So when one licensed professional engineer submits plans to another licensed professional engineer, they either agree or disagree, and either leave it alone or change it. The inspector would then just make sure the project was completed per the submitted plan, rather than to the local code requirements. By the way, usually this is only necessary for large and complex jobs, and usually the design will reference several code requirements to meet.


----------



## geigerr (Sep 28, 2012)

DIYERSCOTT said:


> geigerra said:
> 
> 
> > It doesn’t let me post photos, there are waves in the slab and the texture isn’t consistent. I’m meeting with the company owner on Monday. I’m going to ask for the slab to be removed, and repoured by agreed third party. Seems like a good guy, but we will see what happens.
> ...


I agree, I know where I’m putting the gazebo. Issue is it is one that is put together out of a box. I contacted the company and spoke to many people they don’t have all of the dimensions needed to know actually where I place the footings. They don’t know overhang distance from pilar to roof edge. So my only option would be to build the gazebo’s frame to determine exact dimensions. Now that I have more time this option is possible.


----------



## geigerr (Sep 28, 2012)

One question I got about footings if the slab where the gazebo will be is 8” thick reinforced with rebar, is digging 3 foot footings necessary? Shouldn’t the slab be able to support the 700lb gazebo?


----------



## Canarywood1 (May 5, 2012)

Tom153 said:


> Most codes allow a design to be "out of code", if they are prepared by a licensed Professional Engineer. The reason is because the Licensed professional Engineer is taking personal responsibility for the design, which includes making sure that the project is completed per the design. Usually designs are well within the code requirements; but do not necessarily have to be. If the licensed professional engineer followed commonly accepted engineering design methods, then the design will be as safe as any "code requirement". By the way, the codes are just based on commonly accepted Engineering design requirements, and are generally prepared by licensed professional engineers, and generall the administration of those codes are overseen by licensed professional engineers.
> 
> So when one licensed professional engineer submits plans to another licensed professional engineer, they either agree or disagree, and either leave it alone or change it. The inspector would then just make sure the project was completed per the submitted plan, rather than to the local code requirements. By the way, usually this is only necessary for large and complex jobs, and usually the design will reference several code requirements to meet.





Are you a licensed engineer?


----------



## Tom153 (Nov 10, 2016)

Not anymore. Retired.


----------



## jomama45 (Nov 13, 2008)

geigerra said:


> One question I got about footings if the slab where the gazebo will be is 8” thick reinforced with rebar, is digging 3 foot footings necessary? Shouldn’t the slab be able to support the 700lb gazebo?


Assuming the soil it's sitting on isn't terrible, YES, an 8" reinforced slab is complete overkill for a gazebo.


----------



## Tom153 (Nov 10, 2016)

Depends on your local "frost" depth. The footing should be a bit deeper than the frost depth to prevent differential heaving during ground freezing. You can also mitigate differential heaving by placing well drained base, like gravel underneath the slab. Also, with 8" thick, with rebar, not likely to crack due to differential heaving. Another technique you might consider for a small slab foundation, make the edges locally (about 1 foot wide) deeper than in the middle. One train of thought is that separate footers for a small slab are actually a worse condition, since you then have a slab the floats and an edge that doesn't, which could contribute to differential heave/settlement between the footer and the slab. The center of the slab tends to stay "dry" so no frost heave in the middle. Also matters if the building is heated or not heated.


----------



## jomama45 (Nov 13, 2008)

Tom153 said:


> Depends on your local "frost" depth. The footing should be a bit deeper than the frost depth to prevent differential heaving during ground freezing. You can also mitigate differential heaving by placing well drained base, like gravel underneath the slab. Also, with 8" thick, with rebar, not likely to crack due to differential heaving. Another technique you might consider for a small slab foundation, make the edges locally (about 1 foot wide) deeper than in the middle. One train of thought is that separate footers for a small slab are actually a worse condition, since you then have a slab the floats and an edge that doesn't, which could contribute to differential heave/settlement between the footer and the slab. The center of the slab tends to stay "dry" so no frost heave in the middle. Also matters if the building is heated or not heated.


Did you even take the time to read the original post?

It's a 700# gazebo sitting on a detached patio. Recommending putting frost footings under this thing is absolutely ridiculous, unless you love to pee money and effort away............


----------

