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  1. #1
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    Default OT slab leveling

    I hacked together a small slab jacking injector.
    2" hyd cyl at 3k psi over an 8" mud piston gives about 180 psi of mud pressure.
    (I set the relief of my hydraulic power pack to 3000 psi to protect the injector)

    it pushes about 4 gallons at a stroke through a 7/8" drilled hole.

    the normal jacking mud mix I read about is about 9 parts of sandy soil, 1 part cement, 1 part fly ash. With the purpose of not washing out or shrinking much when drying but still being able to dig through it in the future.

    I did not make a real mix, last night I just pumped muddy black topsoil to test it out.
    Attached Thumbnails Attached Thumbnails mud-injector.jpg  

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    Nice! Let us know how it works once you try it out. I've got a couple concrete stair slabs drooping to one side that would be very useful for.

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    Quote Originally Posted by dsergison View Post
    I hacked together a small slab jacking injector.
    2" hyd cyl at 3k psi over an 8" mud piston gives about 180 psi of mud pressure.
    (I set the relief of my hydraulic power pack to 3000 psi to protect the injector)

    it pushes about 4 gallons at a stroke through a 7/8" drilled hole.

    the normal jacking mud mix I read about is about 9 parts of sandy soil, 1 part cement, 1 part fly ash. With the purpose of not washing out or shrinking much when drying but still being able to dig through it in the future.

    I did not make a real mix, last night I just pumped muddy black topsoil to test it out.
    "Long ago and ..not so far away.." we'd do that with a standpipe about 6 to 8 feet tall, grouted into a core-drilled hole in the slab.

    One would haul pails of the mix up a short ladder, let gravity do the do off the mass in the vertical standpipe. Job done, remove standpipe, grout hole. Worked a treat for patio-sized projects.

    Have a care.

    "Federal Hill" District, Northside Pittsburgh hills about sixty years ago, someone got over-zealous with a grout pump, lifted the seam they were trying to grout in a rock formation, and a rather surprisingly large area of hillside and buildings started to slip and slide, with SERIOUSLY unwanted effects on water and gas lines!


  5. #4
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    Quote Originally Posted by eKretz View Post
    Nice! Let us know how it works once you try it out. I've got a couple concrete stair slabs drooping to one side that would be very useful for.
    It worked really well. I lifted a corner of my slab 1/2" with 3 5 gallon bucket loads. I still have 10 or more buckets go to get the entire slab level but it was getting dark and I just wanted to test it. It is slow compared to a real pump.

    I have run progressive cavity trailer mounted pumps but they are very expensive.

    I looked for a cheap unit and all I could find was this. (a cheaper hand diaphram pump will not make enough pressure) ChemGrout CG5M Skid Mounted Hand Grout Pump

    I had an enerpack, a cheap 2" dia x 12" stroke cylinder from something , some 8" tube scrap, and an UHMW plastic I turned into a piston. I gave the piston a little cup profile around the edge so it would expand upon pressure to seal up.

    This injects through a much smaller hole than your typical 2" diameter. 7/8" is an easy hammer drill size.
    there is a slightly tapered pipe (angle grinder tapered) on bottom that simply sits in the hole.

    The cylinder and piston swings away to load the tube by pouring in a bucket. I plan to strap/mount it all to my hand cart for easy 1 person placement and operation.

    I would recommend. It works great. I will include some more detailed pics tonight.


    (I cannot even imagine a gravity standpipe working unless the bore hole was very large and the mix very soupy)

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    Quote Originally Posted by dsergison View Post
    (I cannot even imagine a gravity standpipe working unless the bore hole was very large and the mix very soupy)
    Gravity was all humankind had, the first few thousand years, so... pretty good track-record, once the "pipe" issue had a solution or three.

    "Soupy", yes, but not as much as one might think. Two other factors far the more important:

    - Retarded setup. Very!

    - "Fines" only. Very!


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    Final details

    Sent from my E6810 using Tapatalk

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    Quote Originally Posted by dsergison View Post
    Final details
    Some flatlanders will go to extreme lengths for the grant of them prestigious "redneck" credentials.

    But she'll do!


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    I was thinking of making one, and wondered if there is an off-the-shelf
    piston.
    Thinking about the cleaning pig a cement pump uses, or some other
    disposable packing.
    Go Devil - Concrete Pump Supply

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    You want to make wet solids soupy,get a concrete vibrator.....the liquid transmits the vibration everywhere it penetrates.

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    What holds the rig to the slab being lifted? I would think the rig would just lift without some way to hold it down.

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    Maximum upward force at that cross sectional area (~0.6 in²) with his stated developed pressure (180 psi) would only be 108 pounds. The weight of the rig is almost enough to hold it down.

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    Quote Originally Posted by digger doug View Post
    I was thinking of making one, and wondered if there is an off-the-shelf
    piston.
    Thinking about the cleaning pig a cement pump uses, or some other
    disposable packing.
    Go Devil - Concrete Pump Supply
    The pigs or foam balls are pushed by compressed air. They sort of just act as a squeegee. If you mechanically pushed them they would deform and bypass due to not having balanced forces on either side of the lip.

    the UHMW piston works super well. I trepanned it a bit so it could expand on the push stroke much like a cup seal. It bypasses air on the return with no problem.


    update: the machine will not pump any amount of "tube sand" mixed in the black topsoil mud. I don't know yet about actual grout mix, but the larger pebbles in tube sand pack up badly.

    In general you should not try to pump concrete with rocks any more then 1/3 your nozzle diameter to avoid packing and jamming. This design is even more sensitive due to trying to flow the mud out an orifice which was just a 1" pipe socket welded to the bottom of the flat plate.

    I'm leveling a 14' x 14' shed slab that was undermined by a groundhog a few years ago. I put about 3 cubic feet under it so far and raised it 1/2" on one side. I have 1" to go.

  17. #13
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    Oh I hate those little devils. I've offed 3 of them in the past couple years. Caught one digging along my basement wall and another digging under the back steps.


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