Post hole
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Joined: Jul 2001
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Post hole
To my engineer friends out there. I am building a fence at my garage and need to solve the following problem: Posthole is 36" deep with a 8" diameter; in the middle of the hole is a square 3.5" post; a bag of ready-mix yields about 2/3 cubic ft. of concrete - question, how much of the hole will it fill?
Back in high school and college (just after the last Ice Age), I took the courses to solve this, but if you don't use it - you lose it.
Thanks.
Dono
Back in high school and college (just after the last Ice Age), I took the courses to solve this, but if you don't use it - you lose it.
Thanks.
Dono
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Joined: Jan 2008
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Post hole
[updated:LAST EDITED ON 28-May-02 AT 04:34 PM (EST)]Hole = 2,304 cu "
Post 31/2"x 31/2" over a 36" length is 441 cu "
Difference of 1,863 cu ".
Concrete bag has = 2/3 of a cubic foot is a square hole 8"x8"x8" =
512 cu "
3.63867 bags of concrete equal 1863 cu "
You need to 3.63 bags to fill the hole to the top.
It appears that 1 bag will fill the hole less than 1/3.
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Post 31/2"x 31/2" over a 36" length is 441 cu "
Difference of 1,863 cu ".
Concrete bag has = 2/3 of a cubic foot is a square hole 8"x8"x8" =
512 cu "
3.63867 bags of concrete equal 1863 cu "
You need to 3.63 bags to fill the hole to the top.
It appears that 1 bag will fill the hole less than 1/3.
[b][i][font color=red]Dennis[/font][i][b]
[font color=red]Calgary,Alberta,Canada[/font]
[link:www.ford-trucks.com/guidelines.html|FTE Moderator]
http://www.clubfte.com/users/mil1ion/Minimorleytruck.JPG
[font color=green] Truck Data Plate Info
[/font
http://www.clubfte.com/users/mil1ion/FordTruckCodes.html
[font color=red]If New Ford Parts Is What You're Cravin',
Then Buy Them HERE,At Motorhaven![/font]
http://www.clubfte.com/users/mil1ion/Mil1ion.html
[font color=red]
Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's" [/font]
[font color=blue]78 F-150 429CJ,Silver,Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
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Posting Guru
Joined: Jan 2001
Posts: 1,124
Likes: 1
From: Rural Florida Panhandle
Post hole
My results differ a little:
Volume of an 8" diameter hole 36" deep =
(volume = Pi*r*r*h, where pi =3.14, r = 4 and h = 36.
This comes to 1808.64 cu in.
The volume of the post is 3.5 * 3.5 * 36 = 441 cu in. (we agree on this)
One cubic foot - 12 * 12 * 12 = 1728 cu in.
If a bag of concrete is 2/3 cu ft then it is 1152 cu in.
Volume of empty space around post = 1809 - 441 = 1368 cu in
Concrete needed = 1 bag and a bit of another.
If I were doing it (and I have) I would put 1 inch of dry concrete mix under the post. This prevents it from ground contact.
In fact I always set my posts with dry concrete mix, then wet it on the top and the moisture in the ground will set the rest.
I may be missing something here -- but that's the way I calculate it.
Winford
Volume of an 8" diameter hole 36" deep =
(volume = Pi*r*r*h, where pi =3.14, r = 4 and h = 36.
This comes to 1808.64 cu in.
The volume of the post is 3.5 * 3.5 * 36 = 441 cu in. (we agree on this)
One cubic foot - 12 * 12 * 12 = 1728 cu in.
If a bag of concrete is 2/3 cu ft then it is 1152 cu in.
Volume of empty space around post = 1809 - 441 = 1368 cu in
Concrete needed = 1 bag and a bit of another.
If I were doing it (and I have) I would put 1 inch of dry concrete mix under the post. This prevents it from ground contact.
In fact I always set my posts with dry concrete mix, then wet it on the top and the moisture in the ground will set the rest.
I may be missing something here -- but that's the way I calculate it.
Winford
Posting Guru
Joined: Jan 2001
Posts: 1,124
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From: Rural Florida Panhandle
Post hole
Glad we could help(er.. confuse) you. Being a country type, I keep a few bags of quick-crete around in the workshop. I'm always needing to use it for something. I installed a fence around part of my back yard. Took 13 posts. Because the soil is mostly limerock, it took and hour to dig each hole, and that was only 24 inches. I put in the dry quick-crete, then wet it with the mister selection on my hose nozzle. Worked out great. That was last year. My back still hurts.
Winford
Winford
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Postmaster
Joined: Nov 2000
Posts: 2,557
Likes: 2
From: Texas
Post hole
I recomended that you dig your holes 2 1/2 ft, pour in 6 inches of pea gravel, set the post on the gravel, then backfill and tamp the soil in firmly.
If concrete is a must, say, for the gate stop or whatever, make sure the bottom of the pole is in the gravel before pouring in the concrete. This will allow the water to drain off the wood.
Leveling of the posts can be accomplished simply by using the tamper on the side that needs to be pushed over.
Also remember to keep your holes as small a diameter as possible in order to let the undisturbed soil be the barrier for the compacted soil. And always put ALL of the dirt back in the hole and build it up to a slight mound around the post to shed off water.
I would not recommend the use of concrete to hold your posts in the ground. The concrete will hold moisture and allow the post to rot much sooner then it would naturally if left in the dirt.
If concrete is a must, say, for the gate stop or whatever, make sure the bottom of the pole is in the gravel before pouring in the concrete. This will allow the water to drain off the wood.
Leveling of the posts can be accomplished simply by using the tamper on the side that needs to be pushed over.
Also remember to keep your holes as small a diameter as possible in order to let the undisturbed soil be the barrier for the compacted soil. And always put ALL of the dirt back in the hole and build it up to a slight mound around the post to shed off water.
I would not recommend the use of concrete to hold your posts in the ground. The concrete will hold moisture and allow the post to rot much sooner then it would naturally if left in the dirt.
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Joe Kucinski
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Joined: Jan 2002
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From: CHEESELAND, USA
Post hole
>I would not recommend the use of concrete to hold your posts
>in the ground. The concrete will hold moisture and allow the
>post to rot much sooner then it would naturally if left in
>the dirt.
Yup then you get to dig out those 2 bags of HARD concrete
>in the ground. The concrete will hold moisture and allow the
>post to rot much sooner then it would naturally if left in
>the dirt.
Yup then you get to dig out those 2 bags of HARD concrete
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