Does cement (Quickcrete, specifically) expand when it cures?

Discussion in 'Off Topic' started by MichaelD, Nov 28, 2003.

  1. MichaelD

    MichaelD Lifer

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    I don't know. Ergo this post.

    Thinking of filling some PVC pipes (3" diameter, 24" long) with cement. I plan on assaulting my next door neighbor...er, filling some speaker stands I'm building.

    If the cement is going to expand, I'll need to leave some "room" at the top and not fill the pipes completely.

    Get busy and answer me. Please. :beer::D
     
  2. Jmmsbnd007

    Jmmsbnd007 Diamond Member

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    Yes. No. I don't know. I'm tired :(
     
  3. KK

    KK Lifer

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    whats it say on the bag?

    KK

    PS. I dont think it expands or you'd have some funky sidewalks.
     
  4. HappyPuppy

    HappyPuppy Lifer

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    Dude, cement is not like water. It does not freeze and expand, it cures chemically. You would have no problem putting it in your PVC.

    I still think you should consider the insulating foam, though.:D
     
  5. vi edit

    vi edit Elite Member <br> Super Moderator
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    If anything, it shrinks a bit. I've help my Dad pour countless foundations and footings and I've never seen concrete expand. The only time it would expand is if it got water seeped into it and it got cold enough to freeze the water. That can make it expand.
     
  6. Amorphus

    Amorphus Diamond Member

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    wait, you're filling the PVC tubing? that just brings the center of gravity up. make a hollow base and fill that.
     
  7. MichaelD

    MichaelD Lifer

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    That's exactly what I thought when I first started researching building my own stands.

    But many folks have explained that since the weight is concentrated straight up and down, and "focused" on one small point (i.e. the end of the PVC) that it makes it more stable.
     
  8. RagingBITCH

    RagingBITCH Lifer

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    Are the pipes going to be in direct sunlight by chance? Concrete does expand and contract, just minimally though.
     
  9. MichaelD

    MichaelD Lifer

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    Hmm...nah, not really. I'm assuming the room will have windows, but it will be climate-controlled. Shouldn't be a problem.

    Quickcrete is sounding better and better. :beer: That's the stuff you just mix with water and be done with it, right? I'll buy one of those disposable "Homer buckets" from HD and a trowel. Done. :cool:
     
  10. huesmann

    huesmann Diamond Member

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    The weight being concentrated doesn't make it stable at all. In fact, if the things tip over, they're more likely to go down than if you didn't fill 'em with concrete simply due to the bending moment of the additional weight.
     
  11. MichaelD

    MichaelD Lifer

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    That DOES make sense. But then how come every stand you can buy, including the VERY expensive "pro" ones are fillable?
     
  12. Shockwave

    Shockwave Banned

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    Dont fully fill it, fill like the bottom 1/3.
     
  13. NutBucket

    NutBucket Lifer

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    Agreed. Make a fillable base instead:)
     
  14. NokiaDude

    NokiaDude Diamond Member

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    You know why they have spaces in-between each slab of concrete on sidewalks? IT'S BECASUE IT EXPANDS WHEN WARM!!!
     
  15. Sukhoi

    Sukhoi Elite Member

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    They probably get filled with stuff to dampen vibrations.
     
  16. RagingBITCH

    RagingBITCH Lifer

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    Very minimally though. That's under 12 hours of direct sunlight. You do see huge cracks in the street sometimes but rarely the driveway. I did mention it above and direct sunglight/heat will not be a problem for Michael. Just chill out.
     
  17. silverpig

    silverpig Lifer

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    Concrete doesn't expand as it hardens. The spaces in the sidewalk are to account for expansion/contraction that it undergoes with the temperature swings of 2 am in January with 1 pm in July.
     
  18. WinkOsmosis

    WinkOsmosis Banned

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    Those cracks are from the soil moving and clay expanding and contracting.
     
  19. KenGr

    KenGr Senior member

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    No, the expansion joints are for the concrete expanding and contracting, not the soil. But it's not a problem on small sections. That's why driveways and streets only have joints every 20 feet or more. Curing doesn't cause a noticeable dimensional change but it does cause a change. When you pour columns and slabs while building a building, the slabs (floors) are supported by shoring (bracing). As the concrete columns harden, some load is taken off the shoring because the columns expand very slightly.

    None of thes has any bearing on speaker stands at all. Just keep the concrete only in the lower part of the stand. AND... DON'T CALL IT CEMENT!!!!
     
  20. MichaelD

    MichaelD Lifer

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    What happens if I call it cement? Does it crack? :D

    Thanks much guys. It has been said that the entire cummulative knowledge of mankind can be found on ATOT. Today has proven this adage correct. :wine::cool:
     
  21. Chaotic42

    Chaotic42 Lifer

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    Yeah, I agree with everyone, put the weight at the bottom. It would be best to have a round base filled with concrete (or sand) and then have the pipe with the speaker on it.

    I'd fill the pipe, because the speaker will vibrate the pipe (especially if the pipe is fastened at the bottom) and it won't sound good.
     
  22. CFster

    CFster Golden Member

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    Don't believe regular concrete expands...

    But they have this stuff called "hydraulic cement" that expands to fill cracks on purpose I heard.

     
  23. Squisher

    Squisher Lifer

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    The reason you want to fill it entirely is to dampen vibrations.

    The only cement that expands when cured is hydraulic cement.

     
  24. tooltime

    tooltime Golden Member

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    i've used it a few times and don't remember that happening
     
  25. Jmmsbnd007

    Jmmsbnd007 Diamond Member

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    Hollow base filled with Quickcrete and have the pipe filled with some kind of vibe-absorber.