#3156205 - 02/08/13 12:29 PM
Construction Q/Concrete
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OldFart
6 Point
Registered: 09/01/00
Posts: 907
Loc: Aurora, CO 80012 USA
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I realize this is way off but I've seen other Qs that are "off" too.
I'm hoping some of you have construction experience, amateur or professional. I'm wanting to pour some concrete to set a 4 X 4 in a hole. Hole is approx 6 in in diameter and 3 ft deep. The purpose is to use the 4 X 4 as a support for a mast used to support a vertical ham radio antenna. See, I told you this Q was off.
I'm wondering about concrete seting up in cold weather. Altho we have had some days lately in 50s, the lows get into freezing down into the teens at night. I have heard that concrete generates heat when curing?? Aren't there additives for the concrete mix to aid in this? I don't want the concrete to freeze or crack and have a big mess on my hands.
Thanks Ray
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#3156240 - 02/08/13 12:58 PM
Re: Construction Q/Concrete
[Re: OldFart]
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TAFKAP
12 Point
Registered: 11/06/09
Posts: 6996
Loc: Memphis
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The additives are referred to as "ad mixtures", and they will allow for a quick setup in less-than-desirable temperatures. But since typical concrete requires 28 days of cure time to develop 100% of its compressive strength, you may want to consider waiting until after the final freeze day.
Another thing to consider would be to utilize some rebar in your foundation. As the antenna sways, it'll generate a tension force in the concrete, causing it to crack and disintegrate.
Another consideration is to not set the wood directly into the concrete. Perhaps a ø6" I.D. PVC pipe set into your concrete will provide the base. You can then separately mortar in the 4x4. That way, when the elements finally overcome the wood, it'll be much more simple to replace the post, rather than the entire footing.
Finally, guy wires will be your best friend.
_________________________
Everything important in life was learned from Mary Jo Kopechne.
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#3156242 - 02/08/13 12:58 PM
Re: Construction Q/Concrete
[Re: OldFart]
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EastTNHunter
8 Point
Registered: 03/08/10
Posts: 1199
Loc: Rhea Co., TN
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Just pour it and cover it with plastic. The ground will provide insulation subgrade, and as you stated, the concrete will provide some "heat" of its own. The plastic should help to keep it from freezing on the top. It should cure slower in the cold, making for a stronger set, in theory.
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#3156255 - 02/08/13 01:12 PM
Re: Construction Q/Concrete
[Re: EastTNHunter]
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OldFart
6 Point
Registered: 09/01/00
Posts: 907
Loc: Aurora, CO 80012 USA
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My final freeze date would prob be in early May. How much do these additives really help? When I dug the hole with a post hole digger the ground was frozen solid about 10 inches down.
Then hit hardpack clay. Only by pouring water into hole, waiting awhile and then digging deeper, did I succeed in getting to 3 ft. Thanks For help! Ray
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#3156265 - 02/08/13 01:19 PM
Re: Construction Q/Concrete
[Re: OldFart]
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Grizzly Johnson
Good ol' Boys "Team Grizzly"
16 Point
Registered: 10/07/08
Posts: 12838
Loc: Mid. TN
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Dig the bottom of the hole out wider than the top.... this will keep the ground freezing/frost creep from pulling the post up out of the ground.
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Bustin' Heads Is Our Specialty
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#3156319 - 02/08/13 02:11 PM
Re: Construction Q/Concrete
[Re: OldFart]
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TAFKAP
12 Point
Registered: 11/06/09
Posts: 6996
Loc: Memphis
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My final freeze date would prob be in early May. How much do these additives really help? When I dug the hole with a post hole digger the ground was frozen solid about 10 inches down.
Then hit hardpack clay. Only by pouring water into hole, waiting awhile and then digging deeper, did I succeed in getting to 3 ft. Thanks For help! Ray
I think your answer will be different, depening on if you're talking to a contractor, concrete salesman, or a concrete finisher. To my knowledge, Redi-Mix guys pretty much tweak their mixtures to the environment they're working in. I think the modern ad mixtures are pretty reliable. But I'm a little old-school when it comes to concrete....(4) ingredients: portland cement, fine aggregate, coarse aggregate, and water.
_________________________
Everything important in life was learned from Mary Jo Kopechne.
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#3156441 - 02/08/13 03:44 PM
Re: Construction Q/Concrete
[Re: TAFKAP]
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in the dog house!
10 Point
Registered: 11/29/12
Posts: 2648
Loc: west tn
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I have been finishing for over 25 years. As long as it isnt below 30 the night after you pour you will be fine. Just cover it with some plastic and hay, and then another layer of plastic. Leave it for 48 Hours and you will be fine. The above post about making it larger at the bottom is a good idea as well as drilling some holes through your post for re-bar to tie the post to the concrete is a must. If you are pouring saccrete I would buy a bag of portland cement to add to it for added strength. You could also a dd calcium carbonate to it to help it to set faster, but not to much or it will weaken the mix, about 2% is max.
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Luck is where preparation and opportunity meet
Μολων λαβε
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#3156620 - 02/08/13 06:34 PM
Re: Construction Q/Concrete
[Re: in the dog house!]
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TRIGGER
Michael Waddell stunt double
10 Point
Registered: 09/25/11
Posts: 2610
Loc: Cunningham TN
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Your hole is not big enough. A 6" hole with a 3.5" square post only gives you 1 1/4" on each side of the post for concrete and less at the points. You need at least 4" around the post in all directions IMO. And your over thinking the temp thing. I poured sixty yards for a driveway today. It's going to be around twenty seven tonight. There will be no problems. If it makes you feel better to cover it it sure wont hurt. With temps in the mid twenties your concrete won't freeze the first night but may the second or third night if the temps stay down.
_________________________
If ever in doubt don't pull the trigger.
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#3156706 - 02/08/13 07:35 PM
Re: Construction Q/Concrete
[Re: TRIGGER]
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BigAl
16 Point
Registered: 07/31/01
Posts: 18814
Loc: Fayette County, TN US
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If you're doing your own mix, just don't overdo the water. The concrete will actually pull moisture from the ground. Too much water and you lose a lot of strength.
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Walls: Leading the way outdoors.
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#3156911 - 02/08/13 10:10 PM
Re: Construction Q/Concrete
[Re: BigAl]
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OldFart
6 Point
Registered: 09/01/00
Posts: 907
Loc: Aurora, CO 80012 USA
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1. Hope everyone has noticed I am in Aurora, CO, a burb of Denver. A bit different fm TN.
2. I will enlarge the hole
3. Can a store like Home Depot or Lowe's cut rebar? It looks like tough stuff?
4. The 9 ft 4 X 4 will have my mast connected by 2 bolts. That way I can pivot the mast to raise and lower it to work on it.
Thanks for all the good info! Ray
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