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the concrete box continued
Posted by: pbarra1
Date: July 06, 2012 02:13PM
The form is done. It is approximately 22x24 and 20 inches high. When filled with concrete I estimate it will be 5 cubic feet of concrete and weigh 750 pounds. I want to keep it the same size but make it about half that weight. Was planning on using the fiber embedded mix to resist cracking. Any suggestions? Can I suspend pieces of foam in the concrete to use less concrete and make it lighter?
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Re: the concrete box continued
Posted by: Frank
Date: July 06, 2012 02:23PM
Don't fill the form to the top? Make it 10" high ... still way too heavy.
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Re: the concrete box continued
Posted by: pbarra1
Date: July 06, 2012 02:27PM
these are the dimensions she wants - no play on that
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Re: the concrete box continued
Posted by: C(-)ris
Date: July 06, 2012 02:28PM
Call someone who works with concrete on a regular basis? Where are you getting the mix from? They should have an idea.



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Re: the concrete box continued
Posted by: Gilbert
Date: July 06, 2012 02:28PM
Foam is used underneath concrete to act as a filler very often. I have never heard of trying to float / suspend it. The challenge would be keeping it in place while the concrete is being poured into the form. You would have to build some kind of cage / structure to hold the foam.

Perhaps others have additional ideas.

Good luck!

EDIT - can you have the foam rest at the bottom of the form or must you have concrete at the base?



Edited 1 time(s). Last edit at 07/06/2012 02:30PM by Gilbert.
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Re: the concrete box continued
Posted by: jdc
Date: July 06, 2012 02:31PM
make the top half hollow?



----


Edited 999 time(s). Last edit at 12:08PM by jdc.
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Re: the concrete box continued
Posted by: billb
Date: July 06, 2012 02:47PM
can you have hollows like concrete blocks ?

foam chunks should be fine if you can stop them from shifting during the pour.
A honeycomb may be more crack resistant





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Re: the concrete box continued
Posted by: pbarra1
Date: July 06, 2012 02:56PM
billb - Are u suggesting putting concrete blocks in the form and filling the voids in the blocks with foam and then pouring in the concrete?
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Re: the concrete box continued
Posted by: macphanatic
Date: July 06, 2012 03:22PM
You should be able to embed stryfoam in the concrete. The real question is how much can you use and not impact the strength of the concrete. You may want to use some rebar to help with the strength aspect.
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Re: the concrete box continued
Posted by: billb
Date: July 06, 2012 03:49PM
Quote
pbarra1
billb - Are u suggesting putting concrete blocks in the form and filling the voids in the blocks with foam and then pouring in the concrete?

no, just suggesting the similar structural elements
small voids (foam blocks or bags) with webs of structural rigidity.

If you go too crazy with sizeable voids you'll need structural reinforcements like rebar.

open at the top like that could introduce animal and freeze/thaw problesm.



+ you could hold blocks of foam in suspension with wooden dowels from above

if you were concerned with water getting in the dowels they could be drilled out after about a inch or so deep and the holes sealed

or build in lifting eyes of some sort to fascilitate moving a heavy solid block



The Phorum Wall keeps us safe from illegal characters and words
The doorstep to the temple of wisdom is the knowledge of one's own ignorance. -Benjamin Franklin
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Edited 1 time(s). Last edit at 07/06/2012 03:56PM by billb.
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Re: the concrete box continued
Posted by: macphanatic
Date: July 06, 2012 04:25PM
You could make lightweight concrete by mixing in perlite.
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Re: the concrete box continued
Posted by: pbarra1
Date: July 06, 2012 04:49PM
perlite - yes but what about the strength. This project is for an 11 foot umbrella that easily blows over a 100 pound base. It has landed on fence and damaged 2 spindles. I want the concrete to look as smooth as possible. I sanded forms and will oil them before pouring. Will the perlite intefere with the smooth look?
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Re: the concrete box continued
Posted by: Carm
Date: July 06, 2012 05:17PM
Besides the fiber concrete mix, I would suggest you make a wire form using the smallest diameter rebar you can get. Make a structure like the one below. Throw in some foam (think water noodles/cheap) or mailing tubes (smallest sonotube I have seen is 6 inches) - vertically. Make sure the foam/tubes have 2 to 3 inches of space around them depending on the mix requirements. The mesh I am referring to is for concrete slaps. It is made of thin wire that is welded together in 4 x 8 sheets. Can be cut and bent.

Here is what I would do.


If you think the mailing tubes will collapse, you can fill them with sand and cap them off at the top. When you remove the form you can drain the sand out through the bottom. I would also put horizontal rebar on top and bottom to keep the tubes/foam in place.

J. Carm



Edited 1 time(s). Last edit at 07/06/2012 05:21PM by Carm.
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Re: the concrete box continued
Posted by: Carm
Date: July 06, 2012 05:23PM
My experience with concrete has been a slab, a base for a table using a sonotube and a concrete table top that was finished with tile and stucco with a firepit on top. Will post picts in a bit.
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Re: the concrete box continued
Posted by: MrNoBody
Date: July 06, 2012 05:24PM
Quote
C(-)ris
Call someone who works with concrete on a regular basis? Where are you getting the mix from? They should have an idea.

agree smiley
Or find a vendor who actually makes architectural precast products.
Like Quick Crete, if you're in California. Just google "architectural precast concrete" for more ideas.



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Re: the concrete box continued
Posted by: pbarra1
Date: July 06, 2012 05:29PM
Carm - The box is 20 inches tall with a toe kick - how many loops of rebar do you suggest?
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Re: the concrete box continued
Posted by: pbarra1
Date: July 06, 2012 05:32PM
MrNoBody - less than 0.2 yards of concrete - well below the min in my area. Doing it all myself
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Re: the concrete box continued
Posted by: C(-)ris
Date: July 06, 2012 06:07PM
Why don't you just dig a hole, use a round tube, and stick the PVC in the middle. Same way basketball hoops and deck supports are done.



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Re: the concrete box continued
Posted by: pbarra1
Date: July 06, 2012 06:13PM
C(-)ris - That would not make for a very functional table. Its an umbrella stand / table
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Re: the concrete box continued
Posted by: bruceko
Date: July 06, 2012 06:16PM
Is it doing anything besides holding your umbrella?
Just make it smaller.
If you get high winds with a super stable base you will probably just break the umbrella.
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Re: the concrete box continued
Posted by: bruceko
Date: July 06, 2012 06:19PM
Ps
if you do use Perlite you need perlite that is designed as a concrete additive. It may be hard to find. you might try to find Agricultural Perlite.
The Masonry fill perlite is treated with silicone. It won't mix well with your concrete.
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Re: the concrete box continued
Posted by: GGD
Date: July 06, 2012 07:12PM
On TV there's always a body or two used as filler in concrete.
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Re: the concrete box continued
Posted by: olnacl
Date: July 06, 2012 08:50PM
Have you considered just getting a longer pole for the umbrella and putting in it the ground? Or do you plan to drag it around the yard?
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Re: the concrete box continued
Posted by: RAMd®d
Date: July 06, 2012 10:07PM
This project is for an 11 foot umbrella that easily blows over a 100 pound base.

Can you compromise in the size of the base? Up to a point, a larger, lighter base would be more effective than a smaller, heavier base. I mean, do you really need a 750lb base.


If you get high winds with a super stable base you will probably just break the umbrella.

I was wondering about that. Was the umbrella deployed when it was knocked over, previously? That would seem like some pretty heavy wind, if it was closed.

Well, what ever is decided, I hope it all works well.




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Re: the concrete box continued
Posted by: Chakravartin
Date: July 06, 2012 10:47PM
Quote
pbarra1
The form is done. It is approximately 22x24 and 20 inches high. When filled with concrete I estimate it will be 5 cubic feet of concrete and weigh 750 pounds. I want to keep it the same size but make it about half that weight. Was planning on using the fiber embedded mix to resist cracking. Any suggestions? Can I suspend pieces of foam in the concrete to use less concrete and make it lighter?

'You looking for something like this?
[www.geofill.com]
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Re: the concrete box continued
Posted by: billb
Date: July 06, 2012 11:10PM
I live in a windy area and have had both furled and unfurled umbrellas knock tables and sand filled base holders over.
What you can buy just isn't robust enough.
I'm not talking leave it out for weeks with total disregard for the weather either, just an afternoon's use.
It's enough of a PITA that our sun umbrella is collecting dust in the garage.
Luckily we have large trees to set up a table and chair under, especially when it is just too hot for the deck anyway.



The Phorum Wall keeps us safe from illegal characters and words
The doorstep to the temple of wisdom is the knowledge of one's own ignorance. -Benjamin Franklin
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Re: the concrete box continued
Posted by: bruceko
Date: July 06, 2012 11:27PM
I come up with 6.11 cubic feet based on you measurements.
We figure about 150# per cubic foot so you are well over 900#
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Re: the concrete box continued
Posted by: billb
Date: July 07, 2012 12:04AM
a basketball in each corner would void about 1 plus a little cubic feet of weight
1 cubic foot =1728 cu in
basketball about 450 cu in each


build 4 basketball sized boxes, one for each corner. square would provide more volume



The Phorum Wall keeps us safe from illegal characters and words
The doorstep to the temple of wisdom is the knowledge of one's own ignorance. -Benjamin Franklin
BOYCOTT YOPLAIT [www.noyoplait.com]
[soundcloud.com]




Edited 1 time(s). Last edit at 07/07/2012 12:06AM by billb.
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Re: the concrete box continued
Posted by: Carm
Date: July 07, 2012 01:01AM
Loops of rebar?? I would use one for each corner, and wire "mesh" folded around the four vertical rebar. Horizontally I would only put rebar on bottom and on top to hold the foam/tubes. If you want to use more rebar its up to you, maybe between the foam/tubes and held in place with the horizontal rebar.


This is the concrete "mesh" i am referring to.

It is easy to bend to support the vertical rebars at the corners. If the openings are in the right spot, you can cut a piece to put on the bottom and top of your form.
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Re: the concrete box continued
Posted by: Carm
Date: July 07, 2012 01:46AM
Here is the table I made. Center is partially hollow and a gas line with a shutoff valve embedded into the concrete. The shutoff opening is on the opposite side.
Base and top are quickrite concrete. Three seperate pours. The top is 3 inch thick quickrite concrete with rebar and wire mesh to keep it together. Base is made from a sonotube 24" if I remember correctly, with a smaller sonotube in the middle to keep it hollow, use less concrete, and make space if I ever wanted to a metal bowl as the firepit. The 24" sonotube has five vertical 1/2 or 3/4 inch rebar for strength and to anchor the top. I chose to go up with the fire on top and used a 3 inch piece of sonotube to make the firepit top.

First pour was the base in the ground for the sonotube. Second pour was to fill the sonotube. Third pour was the table top. Each pour was hand mixed in a wheelbarrow using a shovel. The sonotube swirl marks were covered with stucco and the top was covered with 12x24 grey porcelen tile with glass tile inlays. Sides were covered with individually cut pieces of stone.





Edited 1 time(s). Last edit at 07/07/2012 01:54AM by Carm.
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Re: the concrete box continued
Posted by: Ombligo
Date: July 07, 2012 04:37AM
He is using fiber filled concrete - he shouldn't need rebar and using it wouldn't save weight anyway.

I'd just put either chunks of foam or empty beer cans in it (the latter being developed as the form is made and the concrete prepared).

The house across the street from me was built of foam blocks which were filled with concrete and then skim coated with stucco. You could do something similar. Here is a diagram for a home, the concept is easy to alter.





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Edited 1 time(s). Last edit at 07/07/2012 04:44AM by Ombligo.
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An afterthought: The Umbrella
Posted by: MrNoBody
Date: July 07, 2012 10:03AM
Just curious, is the umbrella vented?
If not (or improperly vented), a skilled canvas tech or sailmaker could add breakout (wind) vents.
Venting would greatly reduce the drag effect of the canopy and properly designed velcroed breakouts would stay closed in light breezes. An 11ft diam is aprroximately 95 sq. ft.; might only require six vents.

thumbsup smiley ...just another alternative to several hundred pounds of ballast.



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Edited 1 time(s). Last edit at 07/07/2012 10:04AM by MrNoBody.
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Re: the concrete box continued
Posted by: pbarra1
Date: July 07, 2012 10:38AM
it is vented
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