How would you remove a concrete pier?

grampastractor · Jul 15, 2012

I need to remove a 6' high 18" thick concrete pier. I have been told that it may be 4' in the ground and is in the center of a 12' square concrete pad that is about 6" thick. To complicate things, it is close to a building and the pad is part of the building.
This is left over from an observatory that was attached to this building. I would like to save the pad if I can and the building!
I was thinking of cutting the concrete 3' from the building and breaking out the rest and renting a hoe to dig out the pier, hoping not to damage the building in the process. I would then need to pour a new pad.
Any better ideas?
Thanks
Don va3any

Brad_Blazer · Jul 15, 2012

Use a demolition hammer to remove the concrete around the base, exposing the rebar, then cut the rebar to remove the column. Chip the concrete away to just below the surface of the pad then trowel some new concrete to smooth it out. A concrete saw might work even better. An engine hoist should work to handle the column as it is cut. The part below ground: leave it.

grampastractor · Jul 16, 2012

Brad_Blazer said:
Use a demolition hammer to remove the concrete around the base, exposing the rebar, then cut the rebar to remove the column. Chip the concrete away to just below the surface of the pad then trowel some new concrete to smooth it out. A concrete saw might work even better. An engine hoist should work to handle the column as it is cut. The part below ground: leave it.

I do not know if it has rebar or not, if not your idea would be even easier. I am just concerned about supporting the concrete column while cutting, when it lets go it will go fast and hard if I don't have it held well enough. Do you think an engine hoist would hold it? I moved a smaller one with the tractor bucket and it seemed like a good load.
Thanks for the help.
Don va3any

vtsnowedin · Jul 16, 2012

Assuming your pier is round the six feet above the floor level weighs 1600 pounds. I'd second the jack hammer and concrete saw method but get a hold of it so it can't fall on your foot. Chain wrapped around and hooked to a good sized loader bucket if you can drive to it or block and tackle, come-a-longs or chain-falls if you can't.

bcp · Jul 16, 2012

grampastractor said:
Any better ideas?

Pillar crane:

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90cummins · Jul 16, 2012

I removed an 18”x18" pier for my chimney using the 3pt hitch on my (small) 650 JD tractor.
First I dug around the pier and down a foot or so I could get a choker chain around it then I attached it to my 3pt hitch and attempted to raise it.
It was quite secure but I slowly moved the tractor back & forth (at idle) several inches or so while applying constant up force.
The constant lift and the rocking slowly pulled the pier up. I had to choke up on the pier a couple times to finally get it completely out of the hole.
It would have taken a huge amount of force to just pull it straight out but rocking it back & forth loosened the soils grip on the footing. It actually came out easier than I thought.

chim · Jul 16, 2012

Concrete is roughly 150#/CF. I figured your 18"ﾘ x 72" pier is less than 1,300#. We handle concrete cylinders on a regular basis. We have an order now for some that are 24" in diameter and up to 10' tall. We lift them using three different methods:

1. Almost all have bolts protruding from the end and start life upright. If we simply want to move them and keep them upright, we have a steel plate with a lift point that gets bolted to the cylinder and we use an overhead crane.

2. When we want to load them on a truck, we choke them with a heavy fabric sling. It is not going to slip as fast as a chain may, and choked about 1/3 down from the top it allows for a smooth transition between vertical and horizontal.

3. We store some cylinders. For that, they are rotated to horizontal using the OH crane and then carried with a yardlift to be placed on 4x4 cribbing (think big tractor with a forklift where the 3PH should be).

At work we do everything we can to comply with safety rules because we don't want to have someone get hurt. Good chokers in like new condition are the best way to lift the loads we are involved with. The only chains we use for lifting are those manufactured with rating tags and they must pass regular inspection (as does all our lifting equipment).

Brad_Blazer · Jul 16, 2012

grampastractor said:
I do not know if it has rebar or not, if not your idea would be even easier. I am just concerned about supporting the concrete column while cutting, when it lets go it will go fast and hard if I don't have it held well enough. Do you think an engine hoist would hold it? I moved a smaller one with the tractor bucket and it seemed like a good load.
Thanks for the help.
Don va3any

You can use your tractor bucket. Keep vertical tension on the column. Assuming it has rebar, leave 2 intact on the side closest to the tractor to act as a hinge and lower the column as you back away. If you are attached near the top you will never have to support much more than half the load or about 1000lb. After it's down cut the remaining rebar. BE AWARE there will be some spring-back in the bent rebar. If there was something mounted on top of a free-standing column it almost certainly has rebar.

Egon · Jul 16, 2012

If you had some therma cord it would get easier!:thumbsup:

But in reality try the jack Hammer. Cut a square on the pad around the pier so the finishing is easier.

grampastractor · Jul 16, 2012

Thanks everyone for the ideas. Looks like breaking/ cutting the pier off is the way to go. I am still a little worried about my tractor being able to control it when it snaps off and I don't think my wife will let me use it as an excuse to buy a bigger tractor.
Thanks again.
Don va3any

CurlyDave · Jul 16, 2012

You can get a small scaffold at HF for ~$150.

If the weight of the column is a real worry start jackhammering at the top and work down.

Daves Maple Farm · Jul 16, 2012

Let my wife on the tractor!

Gary Fowler · Jul 16, 2012

I have never seen a column without rebar. You can find out easy enough with a little bit of chipping. The rebar will be within 3" of the outside of the pier. If it has standard construction, it wil have a least 4 vertical rebars (maybe more) then about every 12" a circular ring will be holding the verts together. You can chip all the concrete away and the column wont fall. I would get a 50# jackhamer and start ringing around it chipping out as big of a chunk as it would break while resting your chisel point on the slab and angle in at a 45 degree. You should see rebar pretty quickly. Assuming it has rebar, chip away all the concrete about a foot wide, then fell it just like a tree by cutting out the rebar on one side on the side that you want it to fall and work around to the back side. It should start to fall over a bit on the second cut if it has only 4 verts. Be extremely careful with the last cut as it will fall quickly when the load exceeds the rebar strength. I would use an OxyAcetylene torch if possible as you can see the steel start to stretch a bit before it fails. With a cut off saw or grinder you wont have any warning and be prepared for it to bounce backward a bit also.
That pier could be anywhere from a few feet below grade setting on a massive concrete slab to more than 60 feet in the ground if it is a friction pile so I would just chip it down 3 or more inches below the top of concrete pad and pour a slab back on top. Leave the rebar in it and bend them over to form and L shape. This will help anchr the concete patch

vtsnowedin · Jul 17, 2012

chim said:
Concrete is roughly 150#/CF. I figured your 18"ﾘ x 72" pier is less than 1,300#. We handle concrete cylinders on a regular basis. We have an order now for some that are 24" in diameter and up to 10' tall. We lift them using three different methods:

.

Check your math.
I get it from
pi *r^2*L* UWT. As the radius is 9 inches or 0.75 ft you get 3.14159 * .75 * .75 * 6 * 150= 1590lbs.

chim · Jul 17, 2012

vtsnowedin said:
Check your math.
I get it from
pi *r^2*L* UWT. As the radius is 9 inches or 0.75 ft you get 3.14159 * .75 * .75 * 6 * 150= 1590lbs.

You've caght my brainphart (3 quarters vs 2 thirds)- I plugged in .667 in lieu of ..75. DUH!

sparc · Jul 17, 2012

vtsnowedin said:
Check your math.
I get it from
pi *r^2*L* UWT. As the radius is 9 inches or 0.75 ft you get 3.14159 * .75 * .75 * 6 * 150= 1590lbs.

What does it matter? The 150 is a ballpark number for estimating. I would take that 1590# and call it 2000 (minimum) for the puspose of sizing rigging, etc.The weight of the actual concrete in his pier will vary from 150lb/cf depending on the aggregate and other components used in the mix, plus the weight of the rebar and/or wire.

I like the engine hoist idea, taking a couple bites you can have it flush with the slab in one or twmanageablele pieces.
Seems like the easiest and least expensive way to go. If you don't have a engine hoist you can rent them by the day, or maybe can borrow from a friend. Worst case buy one at HF and sell it when done for a few bucks less than you bought it for.

vtsnowedin · Jul 17, 2012

chim said:
You've caght my brainphart (3 quarters vs 2 thirds)- I plugged in .667 in lieu of ..75. DUH!

I expected you just hit a wrong key seeing as how most of my computations have one or two on the first try.

vtsnowedin · Jul 17, 2012

sparc said:
What does it matter? The 150 is a ballpark number for estimating. I would take that 1590# and call it 2000 (minimum) for the puspose of sizing rigging, etc.The weight of the actual concrete in his pier will vary from 150lb/cf depending on the aggregate and other components used in the mix, plus the weight of the rebar and/or wire.

I like the engine hoist idea, taking a couple bites you can have it flush with the slab in one or twmanageablele pieces.
Seems like the easiest and least expensive way to go. If you don't have a engine hoist you can rent them by the day, or maybe can borrow from a friend. Worst case buy one at HF and sell it when done for a few bucks less than you bought it for.

What does it matter? Well to a guy that has a tractor that can lift 1500 pounds max a whole lot. All you have to do is look at a few crane failure videos and realise that in every case someboby miscalculated something before the lift. 150 is a pretty good figure for concrete. very few mixes weigh much more then that even including the rebar and not many weight much less then 140 except special light weight mixes for high rise buildings that use light aggregates like pumice.
A good safety factor is good as in being able to lift twice or three times the load but in day to day work with distances and positions often less then ideal most lifting machines get worked at very close to their maximum ability on a regular basis. The question is what do I do if I go to pick this load and can't hold it? Can I drop the load and save myself and the machine or am I committed and failure is not a reasonable option. Best to have that and all the math though through before you pull the up lever.

chim · Jul 18, 2012

It does matter. Mistakes like that can lead to breaking things and hurting people.

While I checked the math twice before posting, I used .667 as a multilplier insted of .75 each time. When I saw vtsnowedin's post I clicked the values into the calculator in inches (3.14 x 9 x 9 x 72 / 144 / 12 x 150 = 1589.625#. It was then that I realized what I'd done.

BTW, we were playing with three 24"Ø x 9' cylinders yesterday trying out some new cribbing ideas for shipping. Having 5T overhead cranes at work kinda spoils you when it comes to moving stuff around indoors.