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




Reply
 
Thread Tools Search this Thread Display Modes
Old 05-02-2012, 09:36 PM  
MoreCowbell
Member
 
Join Date: May 2011
Location: Clayton, NC
Posts: 56
Liked 4 Times on 4 Posts

Default Mixing concrete for column footing

I've posted a number of questions on this forum as I planned for my crawlspace-to-basement conversion project. Most of which were about inane details that I thought were major issues.

Anyway, I am actually doing work on this now. I knocked out the first column, pulled out it's footing and formed out the new footing in it's place (only a little deeper).
Click image for larger version

Name:	DSC_1492.jpg
Views:	1910
Size:	39.4 KB
ID:	3874
The county inspector was out yesterday and gave me his blessing and I will be mixing concrete tomorrow. So, it's time for another question about something that is probably not as significant as I am thinking it is.

I'm using Quickrete pre-mix concrete (the 4,000 PSI product in the yellow bag). My question is how stiff or loose to mix it. I know the ideal amount of water will yield a stiff mix that will take some work to get the air pockets worked out. On the other hand, more water will make the concrete weaker but easier to work out the air.

Should I go with a stiffer mix and just try to work out the air pockets with a 1x2 until I think I got it all? My concern is that I tried that recently with some concrete weights I formed up for a lawn aerator and they looked like swiss cheese when I removed the forms.

Thanks for the input (past and present).



__________________
MoreCowbell is offline  
 
Reply With Quote Quick reply to this message
Old 05-02-2012, 10:01 PM  
mudmixer
Contractor
 
mudmixer's Avatar
 
Join Date: Sep 2006
Posts: 601
Liked 46 Times on 38 Posts
Likes Given: 39

Default

If you have the right slump, any holes (honeycombing) or voids when you remove the forms it is usually due to the placement/vibration and not the low slump.

When dealing with pre-proportioned mixes, you lose the advantages of admixtures that can help, but cannot be used in a DIY job.

With a DIY reinforced spread footing, just use a higher strength (5000 psi) enough water to make placement easier. The major problem with water is the shrinkage and cracking that ios not a problem with a spread footing on grade. Judging by the footing size, depth and reinforcement, concrete strength is not a major factor unless you have huge columns and many stories.

Dick



__________________
mudmixer is offline  
 
Reply With Quote Quick reply to this message
Old 05-02-2012, 10:25 PM  
nealtw
Contractor
 
Join Date: Nov 2010
Location: vancouver, b.c.
Posts: 10,980
Liked 966 Times on 859 Posts
Likes Given: 1650

Default

Throw some fill around your forms, they really are not heavy duty enough to hold the weight.

__________________
nealtw is online now  
 
Reply With Quote Quick reply to this message
Old 05-03-2012, 12:43 AM  
MoreCowbell
Member
 
Join Date: May 2011
Location: Clayton, NC
Posts: 56
Liked 4 Times on 4 Posts

Default

Quote:
Originally Posted by mudmixer View Post
If you have the right slump, any holes (honeycombing) or voids when you remove the forms it is usually due to the placement/vibration and not the low slump.
If you don't have a concrete vibrator, is there a decent alternative? I was using a length of 1x2 making those aerator weights. Is something narrow like rebar a better choice?

Quote:
Originally Posted by nealtw View Post
Throw some fill around your forms, they really are not heavy duty enough to hold the weight.
I'll definitely be packing in some fill as the concrete fills the form. I'm hesitant to do it beforehand since it may cave the form in. The other footings I have to do will be 100% cut into the clay so I will not need to worry about this on those ones.


Thanks for the replies.
__________________
MoreCowbell is offline  
 
Reply With Quote Quick reply to this message
Old 05-05-2012, 11:44 PM  
BridgeMan
Senior Member
 
BridgeMan's Avatar
 
Join Date: Aug 2011
Location: Cottage Grove, Oregon
Posts: 738
Liked 75 Times on 67 Posts

Default

Your forms are too flimsy, and you also ended the rebar too short. Bars should be no more than 2" from exterior concrete faces, while yours look to have more than 3" clear. Hope the stress distribution wedge doesn't crack the unreinforced outsides of the footing.

__________________
BridgeMan is offline  
 
Reply With Quote Quick reply to this message
Old 05-06-2012, 01:31 AM  
MoreCowbell
Member
 
Join Date: May 2011
Location: Clayton, NC
Posts: 56
Liked 4 Times on 4 Posts

Default

My original plan was to mimic the dimensions of the original footing (30x30x10). That would have given me the 2" clearance with the rebar. However, I ended up digging the footing another 2" in each direction to end up with 32x32x12, but the rebar was already cut and I didn't know better at the time.

I'm pretty sure that the original footing was not reinforced anyway (the builder lives down the block from me and he said they usually don't use rebar in the column footings), so I hope that I'll be OK.

At any rate, I poured the concrete a few days ago. I'll wait the full 28 days to get maximum curing before putting weight on it.

BridgeMan, what angle does the stress wedge diverge at? The main reason for deciding to go wider and deeper at the last minute was because I will have a much narrower column than before concentrating the weight (4" pipe vs. 16" block).

__________________
MoreCowbell is offline  
 
Reply With Quote Quick reply to this message
Old 05-06-2012, 11:01 PM  
nealtw
Contractor
 
Join Date: Nov 2010
Location: vancouver, b.c.
Posts: 10,980
Liked 966 Times on 859 Posts
Likes Given: 1650

Default

Weight travels out at 45 degrees, at 10" deep the weight will desperce to 24" for a 4" post. I would use a 6x6 wooden post instead of steal but that's me. You builder down the street is outdated by more that a few years. He didn't buid a footing just a platform for blocks, it had a big footprint so it worked fine but the weight wasn't traveling at an angle.

__________________
nealtw is online now  
 
Reply With Quote Quick reply to this message
Old 05-06-2012, 11:31 PM  
CallMeVilla
Contractor
 
CallMeVilla's Avatar
 
Join Date: Feb 2010
Location: San Diego
Posts: 1,310
Liked 409 Times on 319 Posts
Likes Given: 171

Default

Nobody really answered your question about the slump of the mixture. I'd like to know if there is a field technique for determining adequate slump WITHOUT using a tester. If you eyeball the mixture, it is easy to get it wrong.

Anybody have thoughts? Experience?

__________________
CallMeVilla is offline  
 
Reply With Quote Quick reply to this message
Old 05-07-2012, 01:09 AM  
nealtw
Contractor
 
Join Date: Nov 2010
Location: vancouver, b.c.
Posts: 10,980
Liked 966 Times on 859 Posts
Likes Given: 1650

Default

http://www.gatesconcreteforms.com/pdfs/slumpTest.pdf
__________________
nealtw is online now  
 
Reply With Quote Quick reply to this message
Old 05-08-2012, 10:03 PM  
CallMeVilla
Contractor
 
CallMeVilla's Avatar
 
Join Date: Feb 2010
Location: San Diego
Posts: 1,310
Liked 409 Times on 319 Posts
Likes Given: 171

Default

Interesting slump test . . . Now think of the guy sitting in his basement with one footing to fill and a wheelbarrow of cement. How does he do a DIY field test to get the right slump? Just askin.



__________________
CallMeVilla is offline  
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter DIY Home Repair Forum Replies Last Post
Preparing footing surface for steel column MoreCowbell Bricks, Masonry and Concrete 19 08-29-2012 08:59 AM
Steel vs. Masonry Column Footing Thickness MoreCowbell Framing and Foundation 3 07-24-2011 09:38 PM
Using deck concrete blocks instead of footing foundations lorne17 Decks & Patios 0 02-10-2011 08:25 AM
replace wood column with steel column? Dave928 Framing and Foundation 5 07-05-2008 10:17 PM
problem with column footing bmm9 Framing and Foundation 2 09-22-2006 09:43 PM

Newest Threads

LATEST SPONSOR DEALS