hole in concrete slab for gate

I have an 8 foot gate which opens in the middle. Each gate has a bent bar toward the bottom that is put in a hole in the ground to help keep the gate closed. Recently I had concrete poured in the area and they covered the holes. I want to drill holes into the slab so I can use the bars again. I am concerned that water will get into the holes, freeze, and crack the slab. Is this a valid concern? If yes, what can I do to reduce this risk? TIA Jody
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On 12/29/2004 11:07 AM US(ET), snipped-for-privacy@webmail.co.za took fingers to keys, and typed the following:

Drill the holes deep enough so that they penetrate the full depth of the concrete (4"?) and drain into the stone or ground beneath. Another suggestion is to drill the holes wide enough to be able to insert a short piece of steel pipe into the hole. Any ice will have to expand the pipe before cracking the concrete. Another advantage is that the steel bar won't be banging against the concrete sides of the hole when the wind is blowing.
--
Bill

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willshak wrote:

Suggestion (a) is possible, but more likely to lead to a formation of cavity under the slab near the holes if there is a slope and used much sand...I don't think I personally like that idea too much...
If one were to put the pipe in the hole, I'd recommend using a sealant around the outer edge and have it shorter than the hole depth by a little bit in order to minimize the freeze-thaw around the outer edge and the concrete...
We've got a couple of these in shed driveway areas that have been just a hole that have been there since the barn was built in 1918 and they've not expanded greatly in that time w/ KS winters and being in a corral for the first 50 years of that time before we moved the corrals away from the barn. Since the hole is open on the top the water column simply rises rather than being trapped in narrow cracks such as a wall. On occasion one has to shake the shed door a couple of times to pull the pin, but normally there's not sufficient thickness to make pulling it hard...
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I did this to make a receiver for my two drop pins:
I cut the ends out of a bigger coffee can. I used this as a sonotube. I put two pieces of 1/2" black sprinkler pipe over the bottom of the pins to keep the holes open. I poured concrete around them.
Since you have an existing piece of concrete, you could drill 5/8 or 3/4 holes, insert the short pieces of pipe, drop the pin/s to align, and pour a small amount of pourstone in the void between the plastic pipe and the existing concrete.
As the other poster said, the water will expand, but it will come up, and not go out. If the pin/s are in there, there won't be much water, and your biggest problem may be the pins freezing in the down position, trapped by the water.
Steve
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SteveB wrote:

...
Actually, the plastic is probably a much better suggestion than the metal...and, in thinking about it a little, I'm not so much against the "through the slab" suggestion--w/ just these two small diameter holes the amount of water can't be <that> much...I was recalling a driveway in TN on a steep slope (imagine that in E TN :) ) where the expansion joints allowed a ton of water between the slabs which eroded underneath them...but there was a lot more area for water intrusion.
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