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Old 06-03-2017, 08:15 PM   #1
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Help with Concrete Forms.. Need verification


Hi folks,
I have to pour 10 concrete piers that extend above the ground at various heights from 10 inches to 45 inches and extend below the ground 60 inches.

To save some money, I decided to make the below ground forms out of some 55 gallon drums with the tops and bottoms cut out and the cut edges smoothed and hammered down.

I'm lacking confidence as I'm not very experienced with concrete and have only ever poured slabs.

Using a backhoe, we dug out trenches to depth and "hung" the forms with 2x4s so we could shim them and make them straight and level.

I'm pretty much following jlhaslip's advice on this part the best I can.
The top of the 55 gallon drum has a 2x4 frame built around it and secured with drywall screws. (8 screws total, 2 on each side, screw heads are inside drum but quite flush) Here's a picture of them in the ground after we backfilled:
Note: The top lip of the drum is flush and even with the top of the 2x4's.


Next, I cut out some 1/2 inch OSB board to fit the 2x4 frame on the drums and cut a hole in the OSB so that the sonotube fits through the hole and would be flush with the bottom of the OSB.
Picture of OSB attached to Sonotube with drywall screws. The wood blocks are screwed to the OSB with decking screws. (2 each)

The entire assembly will be screwed to the frames around the 55 gallon drums in the ground and then all of it will be back filled with dirt for extra strength.

Some of the sonotubes only need to extend 10 inches above ground (pictured) and some of them extend almost 48 inches.

Is this going to be strong enough to take a concrete pour? Do I need to do any more work on the forms?

I do intend to provide support to the top of the sonotubes so that we don't knock them around, but at this point, I'm mostly just worried about the pressure exerted on the forms from the concrete itself. We don't want any blowouts.

Thanks for all the help!
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Help with Concrete Forms..  Need verification-drum1.jpg   Help with Concrete Forms..  Need verification-drum2.jpg   Help with Concrete Forms..  Need verification-drum3.jpg   Help with Concrete Forms..  Need verification-drum4.jpg  
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Old 06-03-2017, 08:37 PM   #2
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Re: Help with Concrete Forms.. Need verification


It looks like it should work Ok.
But
How does the sonotube size compare to the drum size? If the sono will fit into the drum I would let the sono hang down into the drum 2 or 3 ". This will keep them aligned.
Or if larger then over the outside.
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Old 06-03-2017, 09:34 PM   #3
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Re: Help with Concrete Forms.. Need verification


The sonotube is about 1.75 inches smaller than the drum. One of the considerations when designing the form was to make sure I did not leave any crevices or grooves where water could enter and freeze. If the sonotube was to extend into the drum and the drum filled up with concrete, there would be a groove where water could settle after the sonotube rotted away.

I plan on removing the wood above grade but I'm just going to let nature rot the drums and the wood away. The sonotube will be cut and removed just a couple inches below grade and the rest can just go to nature.

Opinions?
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Old 06-03-2017, 10:03 PM   #4
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Re: Help with Concrete Forms.. Need verification


I see a possible air bubble developing at the top of the drum, under the O S B, maybe a few small holes drilled in the O S B to allow the drum to fill up.


ED
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Old 06-03-2017, 10:14 PM   #5
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Re: Help with Concrete Forms.. Need verification


Shop Guy..... Don't take my endorsement as anything valid..... but I think you've figured out/ invented a pretty clever pour.

I think you'll be good...

But I have to ask... at those lolly column sizez and depths, is not an engineer and stamp involved....

Can you tell us what you're doing...
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Old 06-03-2017, 11:57 PM   #6
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Re: Help with Concrete Forms.. Need verification


Quote:
Originally Posted by de-nagorg View Post
I see a possible air bubble developing at the top of the drum, under the O S B, maybe a few small holes drilled in the O S B to allow the drum to fill up.


ED
Oh that's a good idea.. I think I'll drill a series of 1/4 inch holes around the edges.

Thanks for the tip... Nice catch!
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Old 06-04-2017, 12:06 AM   #7
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Re: Help with Concrete Forms.. Need verification


Quote:
Originally Posted by MTN REMODEL LLC View Post
Shop Guy..... Don't take my endorsement as anything valid..... but I think you've figured out/ invented a pretty clever pour.

I think you'll be good...

But I have to ask... at those lolly column sizez and depths, is not an engineer and stamp involved....

Can you tell us what you're doing...
I'm installing a ground mounted 8KW solar system. The array is 13 ft wide by 40 feet long.

The reason the sonotubes vary in height is because the array is mounted on a slope.

I provided my township building dept with my custom autocad drawings in 3D with the grade.. I also provided my calculations for load, shear, and moment as well as calculated uplift for 30lb snow loads and 100 mph winds.
He didn't give me any hassles.. even spent an hour on the phone talking to me about his solar ambitions and asking some questions.

In fact, when I turned in the electrical diagrams, the electrical department guy said it was obvious I knew what I was doing and that he'd only require a final inspection.. Huh? That was easy! LOL..

(oh, I'm an engineer myself but do not have a PE stamp)

Here's something that is similar to what I'm doing.. My array is about three times as big and one continuous unit but this picture is pretty close.

I just don't have much experience pouring concrete.. Slabs are just sheets on the ground so its not like I learn much doing it. I mean, how much can you really learn from pouring a pad or a sidewalk eh?
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Last edited by Shopguy; 06-04-2017 at 12:12 AM.
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Old 06-04-2017, 08:55 AM   #8
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Re: Help with Concrete Forms.. Need verification


Looks good from here. Make those air holes bigger, like 3/4 inch so the excess can squeeze out and you can see when the concrete has filled the void.
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Old 06-04-2017, 01:33 PM   #9
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Re: Help with Concrete Forms.. Need verification


Quote:
Originally Posted by jlhaslip View Post
Looks good from here. Make those air holes bigger, like 3/4 inch so the excess can squeeze out and you can see when the concrete has filled the void.
WOW.. 3/4 inch eh? I'll take your advice.. I just would have never thought a hole that big wouldn't cause problems like the concrete leaking out.

I'm starting to get the idea that its not like water or mud in that concrete doesn't flow vertically (upwards) very well.

Saw some youtube videos on the subject of "self consolidating concrete" where it easily flows in such ways.

I obviously have a lot to learn about this stuff..
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Old 06-04-2017, 04:16 PM   #10
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Re: Help with Concrete Forms.. Need verification


I wouldn't make any holes. The void will fill fine with a bit of vibration. Use a hammer to tap it or run an orbital sander with no paper around on it.
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Old 06-04-2017, 04:45 PM   #11
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Re: Help with Concrete Forms.. Need verification


Quote:
Originally Posted by joed View Post
I wouldn't make any holes. The void will fill fine with a bit of vibration. Use a hammer to tap it or run an orbital sander with no paper around on it.
I plan on either buying a vibrator or renting one. I need a nice solid and smooth pour.. especially where it's above grade.

Harbor Freight has one.. not sure if its a piece of junk though..
https://www.harborfreight.com/3-4-qu...tor-34923.html

Or if its only $25 or $30 to rent, I might just rent it. I just hate spending money to rent something if I can buy it and have it forever.
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Old 06-04-2017, 05:04 PM   #12
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Re: Help with Concrete Forms.. Need verification


And once you buy the tool at the same price as renting it, every use after that is FREE.

Just store it well, back in it's original box with the instructions, and shut tight, the tool stays "Fresh as a daisy". And ready to go next time.



I still would use escape holes for the air.


ED
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