My concrete cracks...


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Old 05-17-21, 06:12 PM
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My concrete cracks...

Hi guys. I've been just living with this for a while but if there's a way to fix it, I'd like to. My concrete cracks when I put in fence posts. I use 2x6 posts and about 3 bags of Quickrete, mixed at 5000 psi, which IIRC is like 2 1/2 quarts of water (It's been six months since my last mix). But it always cracks at the corner of the posts. 5000 psi should be tough enough to handle a post without cracking, right?
 
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Old 05-17-21, 06:53 PM
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It probably has more to do with the amount of concrete you are using around the post. The concrete is cracking at its weakest point where it is the narrowest. Making the pour diameter wider and using more concrete will usually eliminate that problem.
 
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Old 05-18-21, 04:41 AM
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First, I have to question using 2x6 for posts. Most 2"x lumber is not treated for ground contact.

I agree with XSleeper. You probably do not have enough concrete thickness around the post, especially at the corners. I've often seen that the concrete needs to be 3 times the diameter of your post.
 
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Old 05-20-21, 02:07 PM
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Maybe so. Here's a picture of one of the least cracked ones. It always springs from the corner of the post, then goes outward. After a year they gap by about 1/16 of an inch. Also, these are 4x6's, not 2x6's. I fat fingered the keyboard.


 

Last edited by 21withagun; 05-20-21 at 02:23 PM.
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Old 05-24-21, 06:39 AM
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So you guys are pretty sure this is just stress cracks? Any way to get it to not happen?
 
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Old 05-24-21, 09:17 AM
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Concrete will almost always crack, you dont stop it, you control it.

In your case you have a big piece of wood in the middle, wood gets wet it expands and concrete cracks!
 
 

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