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Old 09-06-2009, 06:34 AM   #1
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settled sidewalk - help

Hi, my sidewalk is not broken, but settled on one side only (the side near the lawn is fine, but the side near the road is settled by 4 inches). Apart from the settling, its not broken. The settling is pretty much even along the perephery (along the road side).
How do I fix this? Do I have to break/remove the entire sidewalk and then pour the new concrete mix? or can I use the same settled sidewalk as the base and pour concrete (quikrete) over it? What will the problem be, if I do it the this way?
Please give me a solution... thank you all. I had to post this in building & construction as I couldn't get anyones attention in the landscaping section.


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Old 09-06-2009, 06:57 AM   #2
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The problem is likely due to washout under the slab, or laying concrete on uncompacted fill. There is a process called mud jacking where mud is pumped under the slab which raises it. Not sure of the costs, but it may be cheaper to replace the walk, after doing some fill in and a good base.


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Old 09-06-2009, 07:20 AM   #3
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Bill, can I use the settled sidewalk as the base or should I break/remove it and make a new base? I want to use the settled sidewalk as the base, but just want to know if this is okay.
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Old 09-06-2009, 07:27 AM   #4
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As noted by the previous post, the settling is almost certainly caused by one of two problems (possibly both), namely washout of material from beneath the slab, or settlement of the soil beneath the slab. Before deciding on the proper fix, you need to determine the cause.

If washout is the problem, it should be obvious that there is flowing water undermining the slab. You will see evidence of the flow adjacent to the slab. If there is no evidence of washout, move on to potential cause , namely uncompacted soil beneath the slab. This is pretty common, since removal of poor soil combined with compaction of soil takes time and effort, so the step is often skipped, resulting in long term settlement of the soil.

If washout is the problem, you need to replace the soil that has washed out, which generally is easily accomplished by breaking up the slab, then levelling the slab with crushed stone, and placing new concrete. Of course, you need to fix the washout problem, which is generally done by regrading to keep flowing water away from the slab.

In the case where you have settlement but no flowing water, you can remove the slab (jackhammer), excavate the poor soil (poor soil includes silt, soft clay, organic soil, peat, or unconsolidated construction debris), and replace with crushed stone. Compact the newly placed crushed stone, then pour a new slab over it.

Mudjacking is an option, but it only works if there is compacted soil, or naturally occurring soil of adequate strength, near the surface. If you have a 5 foot layer of unconsolidated fill, for example, mud jacking is not going to work well, and you will need to remove the entire thickness of bad soil.

Assuming you break the slab up, there is no reason you can'tuse the concrete pieces as part of the replacement fill soil. It works fine if you crush it into small pieces, say less than 1 inch diameter on average, and compact it adequately.
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Old 09-06-2009, 06:47 PM   #5
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Dan's idea of using your old concrete as a part of the new fill is a good one, if you can bust it up small enough-OR: look in your local phone book, ask around for a contractor who has equipment that will grind up concrete into "crush and run" , or small concrete pebbles. We have one local contractor who will take your concrete by weight, and sell you "crush and run" by weight cheap for bringing yours in. Sort of paying him to crush it. It's a really good deal in our area. Good Luck, David
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Old 09-07-2009, 06:29 AM   #6
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here's what we did once - saw'd the sidewalk full-depth at the joints & then used a crowbar to lift separated sections while someone else placed 3/8" crushed stone under the low side,,, because the soil wasn't sufficient to 'hold' the walk, had to do it again about a yr later,,, im-n-s-h-fo, much cheaper & easier than the previous suggestions.


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