DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Bricks, Masonry and Concrete > Mixing concrete for column footing





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Old 05-08-2012, 09:30 PM  
nealtw
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Follow instruction on the bag.



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Old 05-09-2012, 03:46 PM  
MoreCowbell
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Well, it turned out OK after all (I think).

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I was mixing batches of about 2 cu.ft. at a time in my small mixer. I didn't use any slump tester, just eyeballed it. The first couple batches were probably stiffer than normal and the last few probably a little looser than they needed to be. In any case, it's been almost a week now and I'll probably wait the full 28 days before taking my temporary supports out and putting weight on it.

Nealtw, I think I'm safe with that 45 deg stress cone. There is 14 inches between the column and the edge of the footing. Including the 3.5" curb on top, I have 15.5" of concrete depth.

Now, just 4 more to go.

Thanks for all the input.



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Old 05-10-2012, 09:27 AM  
mudmixer
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Cowbell -

You do not have to wait the fictitious 28 days. That number is only for standard laboratory testing procedures and they frequently test much more often and after a couple of days you will have 70% of ultimate and your loads are no where high enough to have to wait.

Your soil was warm and you are buried, so the conditions for curing are good.

Dick

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Old 05-11-2012, 06:16 PM  
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In 14 days, you get 80% strength. In 28 days, you reach the 100% strength. In reality, you have to make the call.

Here is a curve which gives you a strength versus time curve: http://www.ce.memphis.edu/1101/notes/concrete/section_3_properties.html

Nice job on the pour. Good to see quality work being done out there.

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Old 05-11-2012, 09:09 PM  
MoreCowbell
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Quote:
Originally Posted by mudmixer View Post
Your soil was warm and you are buried, so the conditions for curing are good.
Well, I was iching to remove the temporary supports and get the weight on the new column. You gave me that last push. I did that a few hours ago. That made 8 full days of curing. It looks like it's supporting the weight just fine.
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Thanks for all the tips.
-Rob
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Old 05-11-2012, 09:34 PM  
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Regarding slump (although too late now), if he's really anal about it, he will acquire a K-slump tester. It's a handy little device that you poke into a pile of concrete, and it immediately gives you a slump reading. Uses a calibrated, perforated hollow tube that lets the mortar in the mix flow into the tube. Paid around $25+ for mine 30 years ago (made in Canada, as I recall), so they're probably double that by now.

If he decides to "guesstimate" his slump, placing a shovel-full of mud (on a dry surface) that almost stands up by itself will be good-to-go. Somewhere between 2" and 3".

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Old 05-15-2012, 01:56 AM  
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interesting...



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