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Old 04-29-2009, 12:14 PM  
PearlWhiteGT
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Default Poor Construction (Pics)

Is there any way to make this look better or fix it? I plan on laying tile over the patio floor but can't stand that the column is hanging over the concrete & the other one isn't. Took a pic of both sides so that you could see what I am talking about.

I'm thinking of just connecting a other piece of slab with rebar all the way to the end of the wall. Just not sure if it will look good with the rest of the house since it won't be covered. I could use that extra area for my bar-b-que pit. I want my patio for entertaining. So what do you guys think? Any other advice would be Great too!!!





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Old 04-29-2009, 01:42 PM  
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The question is not how this happened but, why was it not made correct?
In my opinion, the fix is not worth the results however, instead of pouring more concrete, consider downsizing the columns. Good Luck.



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Old 04-29-2009, 09:20 PM  
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Those columns aren't supporting any serious weight like the teleposts in your basement are (if you have a basement) so it's not a structural issue. It's really just an aesthetic issue.

Chaulk one more up to "Dumb A$$ Mistakes".

Can you contact your builder and have it fixed?

I wouldn't make that end pillar narrower; I would add concrete to the edge of the patio as you were thinking. But, you wouldn't use short pieces of rebar to pin the new concrete to the old.

You would quite literally glue the additional concrete to the edge of the patio with something called a "concrete bonding agent". Concrete bonding agents are very similar to white wood glue, except that they have a "window of opportunity" (typically several hours to two weeks) after applying the concrete bonding agent to the old concrete during which you can apply the fresh cement mix to the concrete bonding agent. During that window of opportunity, the moisture in the fresh cement will reactivate the concrete bonding agent so that the fresh cement sticks to well to the concrete bonding agent (which itself is sticking to the old concrete. Once that window of opportunity is over, a chemical reaction occurs in the concrete bonding agent which renders it waterproof so that moisture will no longer re-activate it. Once that window of opportunity is over, then the new concrete is stuck to the old concrete for good. You'd need to use a cold chisel or sledge hammer to get the new concrete off the old stuff.

I have done exactly that using a concrete mix made by the Grace company called "Daracrete" and Grace's concrete bonding agent (called Daraweld "C"). It's not hard to do because Daracrete is "shape-able", like drywall joint compound, when it's wet. I'd say your best bet would be to excavate to below the slab on that side and place two boards fastened edge to side to make an "L" shape "trough" closed off at the end that you can slip under the edge of the patio slab. I'd pack under it to hold it in place and drive some stakes in the ground outside of that L form to prevent it from moving away from the patio. Paint the inside surfaces of your form with a thin coat of new or used engine oil so that the concrete won't stick to the wood. Then, paint your concrete bonding agent onto the edge of your old concrete (where ever you want the new concrete to stick) and start filling up that form with Daracrete. Cover the fresh Daracrete with plastic, stapling it down to the top of the form and weighing it down with a board or even mud on the patio. The plastic will prevent moisture from evaporating from the concrete, making it cure harder and stronger. The form will hold the cement in place until it cures into concrete, the concrete bonding agent will glue the new concrete to the old as it dries.

You might have some trouble getting the concrete under the pillar. If it was me, I would start at the pillar end so that you can reach your arm into there a bit and pack the Daracrete upward to stick to the bottom of the pillar, or anything there is to stick to under there. If that pillar has hollow spots on the bottom, I'd put a piece of duct tape or sheet metal under it to stop the concrete from going up into it. And, once that concrete is cured and you pull the sheet metal out and the form off, I'd caulk around that pillar base to keep water out of there. I'd use the Sika company's Sikaflex 1a moisture cure polyurethane caulk for that.

Any small concrete contracting company could do this for you as well.

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Old 04-30-2009, 04:39 AM  
PearlWhiteGT
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Originally Posted by Nestor_Kelebay View Post
Those columns aren't supporting any serious weight like the teleposts in your basement are (if you have a basement) so it's not a structural issue. It's really just an aesthetic issue.

Chaulk one more up to "Dumb A$$ Mistakes".

Can you contact your builder and have it fixed?

I wouldn't make that end pillar narrower; I would add concrete to the edge of the patio as you were thinking. But, you wouldn't use short pieces of rebar to pin the new concrete to the old.

You would quite literally glue the additional concrete to the edge of the patio with something called a "concrete bonding agent". Concrete bonding agents are very similar to white wood glue, except that they have a "window of opportunity" (typically several hours to two weeks) after applying the concrete bonding agent to the old concrete during which you can apply the fresh cement mix to the concrete bonding agent. During that window of opportunity, the moisture in the fresh cement will reactivate the concrete bonding agent so that the fresh cement sticks to well to the concrete bonding agent (which itself is sticking to the old concrete. Once that window of opportunity is over, a chemical reaction occurs in the concrete bonding agent which renders it waterproof so that moisture will no longer re-activate it. Once that window of opportunity is over, then the new concrete is stuck to the old concrete for good. You'd need to use a cold chisel or sledge hammer to get the new concrete off the old stuff.

I have done exactly that using a concrete mix made by the Grace company called "Daracrete" and Grace's concrete bonding agent (called Daraweld "C"). It's not hard to do because Daracrete is "shape-able", like drywall joint compound, when it's wet. I'd say your best bet would be to excavate to below the slab on that side and place two boards fastened edge to side to make an "L" shape "trough" closed off at the end that you can slip under the edge of the patio slab. I'd pack under it to hold it in place and drive some stakes in the ground outside of that L form to prevent it from moving away from the patio. Paint the inside surfaces of your form with a thin coat of new or used engine oil so that the concrete won't stick to the wood. Then, paint your concrete bonding agent onto the edge of your old concrete (where ever you want the new concrete to stick) and start filling up that form with Daracrete. Cover the fresh Daracrete with plastic, stapling it down to the top of the form and weighing it down with a board or even mud on the patio. The plastic will prevent moisture from evaporating from the concrete, making it cure harder and stronger. The form will hold the cement in place until it cures into concrete, the concrete bonding agent will glue the new concrete to the old as it dries.

You might have some trouble getting the concrete under the pillar. If it was me, I would start at the pillar end so that you can reach your arm into there a bit and pack the Daracrete upward to stick to the bottom of the pillar, or anything there is to stick to under there. If that pillar has hollow spots on the bottom, I'd put a piece of duct tape or sheet metal under it to stop the concrete from going up into it. And, once that concrete is cured and you pull the sheet metal out and the form off, I'd caulk around that pillar base to keep water out of there. I'd use the Sika company's Sikaflex 1a moisture cure polyurethane caulk for that.

Any small concrete contracting company could do this for you as well.
I was told to use rebar because I'm in South Texas & we always have really bad foundation problems here. I had planned on laying some sort of nice tile on the patio floor as well & don't want to worry about the tile cracking later due to that part of the addition. What do you think?

BTW, thanks for the great info!!!
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Old 04-30-2009, 12:44 PM  
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I should advise you that I'm no expert in this field, I have only done this kind of work when building a floor in a storage room which formerly had a mud floor. The concrete walls in that storage room were rough concrete, and I wanted to install 2X12 floor joists on 12 inch centers. So I attached 2x4's to the walls, and then used those 2X4's as screeds to establish a smooth flat section of Duracrete along the base of those concrete walls. I then used powder charges to fasten 2X12 headers to that section of Duracrete and used steel joist hangers to hang 2X12 floor joists between the two headers. I built that floor 20 years ago, and it's solid as a rock.

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I was told to use rebar because I'm in South Texas & we always have really bad foundation problems here.
The person that told you that doesn't understand the very first thing about concrete... and that is, fresh concrete will not stick to old concrete the way new paint sticks to old paint. So, you use rebar where you want to pin slabs of concrete together so they don't move relative to one another.

For example, if you wanted to pour a concrete slab for your patio, you would drill holes in your house's concrete foundation, probably use epoxy to glue short pieces of rebar into those holes, and then pour the concrete slab for the patio so that those rebar "pins" would be encased in that concrete patio slab. That would prevent the slab from moving away from the house or moving relative to it. If frost heave (which you probably don't have in Texas) were to lift the concrete slab a few inches up, it would still remain pinned to the house foundation so that the slab rising wouldn't prevent you from opening a door that opens onto that slab. But, the slab wouldn't be bonded or glued in any way to the foundation because new concrete won't stick to old concrete.

If you were to use short pins in your case, the new concrete would stick well to the pins, but it wouldn't bond to the existing slab. So, if you were to step on the new concrete between two pins, that concrete would probably break under your weight.

To do what you want to do, you need to glue new concrete to old, and you use a concrete bonding agent to do that. Basically, it's polyvinyl acetate glue (chemical name: Elmer's White Wood Glue) that has a bit of chemical wizardry built into it. The glue can dry, but after a certain length of time in that dried condition, moisture will no longer re-emulsify it so that it remains permanently unaffeced by moisture. During that window of opportunity, however, moisture will re-activate the glue so that anything wet will bond to it. Fresh concrete, with it's high moisture content will re-emulsify that concrete bonding agent during it's window of opportunity so that the fresh concrete bonds to the bonding agent, which is already bonded to the old concrete, thus sticking everything together. Then, as time goes by and the window of opportunity passes, that chemical transformation takes place in the concrete bonding agent so that it is no longer affected by moisture.

So, if you were to use small pieces of rebar between the new concrete and the slab, the pins would hold the concrete to the slab only at the pin locations. But, because concrete is weak in tension, of you were to stand on the new concrete between two pin locations, your weight could very well be enough to break that new concrete piece the pins are holding in place. By gluing the new concrete to the old with concrete bonding agent, then the whole new piece is glued to the old slab so that it can support weight all along it's length.

Google "concrete bonding agent" and you should find lots of different products available in your area.

You don't need to know the rest:
That chemical wizardry is merely the formation of crosslinks between and within the PVA (polyvinyl acetate) resins in the concrete bonding agent. Polyvinyl acetate is known better as white wood glue, and one of it's characteristics is that it re-emulsifies (dissolves, kinda) in water even if it's been dry for years. (This is in fact how furniture repair shops take glued joints apart on broken furniture, by getting the glue wet if its PVA glue.) When crosslinks form within and between the various PVA resins in the glue, then those chemical bonds between resins both prevent those resins from softening and changing shape, and from floating off into the water around them, and that makes the PVA glue waterproof as the window of opportunity closes.
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Old 04-30-2009, 08:08 PM  
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Hello PearlWhiteGT:
I have done extensive concrete work, reinforcing and forming. The epoxy bonding agent is necessary to make a good, lasting job but I would add a U-shaped #4 rebar, 4 to 6 inches wide on 2' intervals, drill them into the existing slab and secure with epoxy, then one single rebar the length of the new work to tie the U's togather. Make sure none of the steel comes within 1" of your concrete forms or the surface, the sun would pop them out later.
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Old 04-30-2009, 11:07 PM  
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This the first I've heard of epoxy concrete bonding agents. I expect they'd be a lot stronger than PVA (white glue) based concrete bonding agents. If it wuz me, I'd use an epoxy concrete bonding agent instead.

I'm presuming he can buy those U shaped hoops at any place that sells rebar?

I'm wondering if painting the epoxy bonding agent onto the side of the slab isn't gonna be a problem with that one long rebar in place. The new concrete looks like it's only going to be 4 inches wide and 6 inches deep or so. With the rebar through the middle of that space, I'm thinking he can use one of those small paint rollers that's four inches wide and only an inch or so in diameter. You can get fairly long handles for those to paint behind toilet tanks.

I'm also wondering if this wouldn't be the ideal place to use that concrete with the tiny fibers in it. Can't remember what it's called, but it has tiny fibers (fiberglass or carbon fibers, maybe?) in it that act like tiny rebars throughout to hold the concrete altogether so it doesn't crack. Is there any reason not to use this kinda concrete with rebar?

I'm thinking if it wuz me, I'd drill and epoxy the hoops into the edge of the slab and have one rebar running the whole length of the pour as Glenn suggests wired to those hoops with steel (or any kinda wire) and have the epoxy bonding agent unmixed but ready. But then,...

...have the actual pour done by a small concrete contractor with that cement with the fibers in it. It may be a problem getting the concrete under the overhang of that pillar, but someone with lotsa experience is going to do a better job than someone without. This is your house and it's your biggest investment, and screwing up with concrete is a permanent screw up. You can save 90 percent of the cost of repairing and maintaining your home by doing things yourself, or at least making the attempt cuz often it's simple stuff that's causing the problem, like dirt in places where it matters. I'd consider this project of of the remaining 10 percent that's best left to a pro just cuz of the permanence of any mistakes made pouring concrete.

I think it would be best to put the hoops in yourself and fasten a piece of rebar to those hoops with wire (any kind). But, for the actual pouring, I'd have a pro do that.


PearlWhiteGT:
If you do put either the U shaped rebar hoops or short pieces of straight rebar into the edge of your slab, you'll need to rent a special drill called a "rotary hammer" for an hour or two. Rotary hammer drills use a piston and cylinder arrangement to drive the drill bit forward and back about 1/8 inch on each rotation, so they have a much more powerful battering action than "percussion type" hammer drills. Also, concrete is much harder and stronger than brick mortar, brick or concrete block, so even though you can drill small holes in these other materials with your small hammer drill, you won't be able to drill larger (like 1/2 inch diameter) holes in concrete with it.

You don't need to know the rest:
Rebar can certainly be used the way Glenn is suggesting; to simply hold the concrete addition together. Really, however, it's best used to strengthen concrete. The way they do this is (in the case of a slab of concrete) by adding a layer of rebar near the top of the slab and another near the bottom of the slab. In this way, you create a structure similar to drywall. In drywall, paper is very strong in tension, but it stinks in compression. that is, you can pull awful hard on a sheet of paper without tearing it apart, but it's awful easy to crumple up a piece of paper. By having paper glued to each side of a 1/2 inch thick gypsum "slab", then for the drywall to bend, then the paper on one side or the other of the drywall has to actually stretch. It's the strength of paper in tension that prevents the paper from stretching and gives drywall it's rigidity.

To strengthen concrete, you do exactly the same thing by putting a network of rebar at the top and bottom of the concrete slab. Concrete is awful strong in compression. You can put an awful lot of weight on top of a concrete block, but it's relatively weak in tension. If you pull on that block to stretch it, it'll break without too much pulling. So, by using two layers of rebar; one at the top and one at the bottom of the concrete slab, then for the slab to bend, then the steel rebar on one side or the other of the slab has to stretch. Steel is very strong in tension. They make chains and aircraft cable out of steel because it's so strong in tension. So, with the rebar network at the top and bottom of the slab, the steel on one side or the other has to stretch before the concrete slab will bend. That makes the concrete slab very much more rigid so that it can support very much more weight without bending. So, without using any stronger concrete, you can make a slab behave as though it was made from stronger concrete (cuz of that steel rebar carrying all the bending forces). For sure, there are stronger and weaker "cements", but in this case we're making an ordinary cement behave as though it were much stronger by using steel rebar to reinforce it so that it doesn't bend.

In this case, we're not strengthening the concrete at all by putting a single rebar through the middle of it. That rebar serves only to keep the concrete addition together (in one piece).

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Old 05-01-2009, 06:33 AM  
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I assume this is a new house, or new to you? I would just go get a BBQ grill, invite some friends over, have a beer or two, grill some steaks and live life. No one will notice and you will soon forget about it. Its not a structural issue.

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Old 05-01-2009, 08:00 AM  
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There is wisdom in Handyguy's words. If this turns out to be the greatest source of stress in your life, you'll be as content as Buddah.

Quite honestly, if it wuz me, I'd do exactly as Handyguy prescribes. Fire up the barbie, have a steak with your friends and neighbors and blame it all on the dog. Tell guests that your black lab never could add dimensions. Call it a conversation piece.

Or, fix it.

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Old 05-01-2009, 10:06 AM  
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Hello PearlWhiteGT:
I have done extensive concrete work, reinforcing and forming. The epoxy bonding agent is necessary to make a good, lasting job but I would add a U-shaped #4 rebar, 4 to 6 inches wide on 2' intervals, drill them into the existing slab and secure with epoxy, then one single rebar the length of the new work to tie the U's togather. Make sure none of the steel comes within 1" of your concrete forms or the surface, the sun would pop them out later.
Glenn

Excellent post..I would add that you should compact the soil in that area. After tiling it should look sweet...post pics when your done

Tom


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