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Old 08-01-2005, 05:23 AM
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Default Concrete question, underpinning

I opened a real can of worms with this combo deck / patio project. When I started to remove the old slab (2") that had slates sunk in it, I realized what a past owner had done. They had brick veneer wall installed on the one wall of the house that wasn't brick from the get go. They built it on top of this 2" slab and that explains the cracks I saw in some of it So I have to jack, support and do the footings that it should have had alittle at a time. So the question.
I take it that concrete shrinks some on curing?, is there a strong product that can be pored that, if anything, when cured might expand a tad?
All I can think to do at this point is to pour my deep footings, then make a jack that can be buried in the final pour of concrete under the wall. Angle iron, rod couplings, bolts and a flat plate as a foot for the jack.
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Old 08-01-2005, 06:25 AM
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Hi Wayne, there is about a bazillion nonshrink grouts on the market. I can’t ever remember dealing with any that expand, I would think that would be hard to predict. Another thing you might look at doing is pour your footing then hard shim the wall with flatbar, or anything out of steel. Just remember to have plenty of concrete coverage around the steel, or your concrete will crack. I can’t ever remember seeing it spec’ed out for less than 2-inches of coverage, most cases it’s 3-inches. What I would consider doing is pouring your slab, hard shim the wall, and then pour a topping slab to incorporate the wall and shims into the nonshrink grout. Here is a link to EMBECO’s web site. I have used their grouts before when setting machinery

http://www.unicon.ca/Chemrex/embeco_636_plus_grout.htm
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Old 08-01-2005, 08:14 AM
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Quote:
Originally Posted by Pile Buck
Hi Wayne, there is about a bazillion nonshrink grouts on the market. I can’t ever remember dealing with any that expand, I would think that would be hard to predict. Another thing you might look at doing is pour your footing then hard shim the wall with flatbar, or anything out of steel. Just remember to have plenty of concrete coverage around the steel, or your concrete will crack. I can’t ever remember seeing it spec’ed out for less than 2-inches of coverage, most cases it’s 3-inches. What I would consider doing is pouring your slab, hard shim the wall, and then pour a topping slab to incorporate the wall and shims into the nonshrink grout. Here is a link to EMBECO’s web site. I have used their grouts before when setting machinery

http://www.unicon.ca/Chemrex/embeco_636_plus_grout.htm
I can't believe I didn't remember the grout myself as thats what the laborers poured into large pump bases after we set them and the mill wrights aligned the couplings.
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Old 08-01-2005, 08:26 AM
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Quote:
Originally Posted by wayne64
I can't believe I didn't remember the grout myself as thats what the laborers poured into large pump bases after we set them and the mill wrights aligned the couplings.
YUP!,,,,,,,,,,,,,,,,,,,
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Old 08-01-2005, 08:28 AM
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I repaired a collapsed concrete block foundation with chink bottle jacks holding the structure. The concrete truckdriver asked how I was going to get the jacks out I tol't him that they were about $8 each and he could have them if'n he wanted to chip them out after the cement set.
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Old 08-01-2005, 09:09 AM
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Default i,m a building contr.

a 2" slab is way too thin. it can,t support itself, longterm. not to mention anything else. we need pix or drawings! not enough info to give any real assesmemt
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Old 08-01-2005, 09:17 AM
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I have never seen or heard of an expansive crete. It wouldn't have a wide range of application due to the expansion. I can just see my finishers now if the concrete started rising out of the forms! It would be hilarious...until you had to fix the mess.

All I can suggest is a non-shrink grout. Some of them are very good. The one Homey Despot sells isn't bad at all.
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Old 08-01-2005, 10:07 AM
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What about hydraulic cement? Or is that the same thing you're calling "non-shrink grout"?

I had a call to patch a shower floor several years ago & had no clue what to use. It was one of those one-piece molded floors that looks like epoxy with some little aggregate pieces mixed into it. There had been multiple attempts to caulk it, none successful. So I began a line by line yellow pages search by phone & eventually came up "hydraulic cement". They said it would work because it expands when it cures but I would have to buy a 5 gallon bucket. So I did, cost about $40, I used about a coffee can full of it and it worked, much to my surprise. I still have the bucket in storage - I think. I can get the product name & number off of it if you want it.
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Old 08-01-2005, 10:08 AM
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We just added a concrete patio to our house that replaced an old wooden one. When we tore it out we found that the footing supporting one of the walls for the carport had fallen about 3". I could fit my arm between the footing and the wall. It is a log house so it was semi self supporting.

We jacked the outer end up and I put a consumable stainless jack in place and poured around it. The trick for getting the concrete to flow under the wall successfully was to use a rod type vibrator. Just touching the vibrator to the concrete made it flow under like water. We are very happy with how it worked out. I can post some pics if you are interested in seeing it.
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Old 08-01-2005, 11:46 AM
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Hi Mongo, those are called pencil vibrators, 99.9 % of them require a high cycle generator. If you plug them into regular 120-volt, in just a few minutes you’ve bought your self a vibrator. I’ve had more than a hundred occasions to write out the PO because some one didn’t think to ask With small pours sometimes your better off with a rubber mallet than a vibrator, most guys, myself included over vibrate. Next time you see a concrete wall, if it has little holes in the surface, most likely it has been over vibrated. General the city of ?, the state of ? the Port of ? will just pitch a fit over this.
Kevin using this nonshrink grout you can pour a 2-inch think, or less slab with this stuff no problem. It’s used under machinery everyday. When I was a Millwright apprentice I did a lot of pump bases and so on.
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