Casting concrete parts? Additives? Fibres?

  1. julianf

    julianf Member

    Messages:
    3,236
    Location:
    devon, uk
    In relation to my other thread, im missing some concrete sections of my garage.

    Im wondering if i cant re-cast some more, using the existing parts as patterns?


    Here are the photos again -

    Inside face -

    [​IMG]

    Outside face -

    [​IMG]


    Now i dont care about the textured finish at all, so im thinking of gettng a sheet of wood, screwing some "shutters" to it for the flat sides (on every part, two sides are completely right angle, and two sides are profiled) and shaping a batton to the profile, and screwing that down too.

    Then probably lay some polyethene down, just to act as an easy mould release.

    I reckon that would work, but what sort of mix should i use?

    This is only a single story garage. Ill probably put my sections on the upper row, so the load will be minimal, but should i try and acquire fibres (dont even know where to buy them - ebay i guess?)

    ...or just make up a standard mix - say 1:4 cement / all in ballast?

    What do you think?
     
  2. eLuSiVeMiTe

    eLuSiVeMiTe Member

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    Dont they have rebar in like concrete posts and gravel boards?
     
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  3. TechnicAl

    TechnicAl Member

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    I tried to smash some up....they have wire reinforcement in them....or mine did anyway....I was hoping to use it for ballast...had to get a skip....but it was years ago when a skip was cheaper than a garage
     
  4. roofman

    roofman "Hey!! calm down calm down"

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    As far as i am aware people cant give these sectional garages away..in fact i am dropping one next week for a customer with perfect panels that you could of had but distance is our enemy julianf:(
     
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  5. brightspark

    brightspark Member

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    yep only thin ish stuff though about quarter inch rod 4 length to a panel
     
    Last edited: Oct 11, 2018
  6. julianf

    julianf Member

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    I can tell you with absolute certainty that mine do not have mesh in them....
     
  7. gaz1

    gaz1 Member

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    I got mine for free and on top of that I got another 3 free ones for others in my area
     
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  8. julianf

    julianf Member

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    And if you wanted to cast some replacement panels, how would you do that.... ?
     
  9. gaz1

    gaz1 Member

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    In mine they was 3mm or 4mm bars

    I'd make a former using wood and plastic sheet but make the middle seperate easier to remove from mold but longer so bars can inserted then using a ads drill tap a little on mold to settle the mix but not too much

    You need it wet but not over wet too much water on surface start again

    Use plastic for through holes easier to drill out when set or pull out when mold going off
     
  10. bigegg

    bigegg I drink and I know things. Its what I do.

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    I'd go for a 3:1 mix, no aggregate, just rough sand.

    chicken wire for the reinforcement, cast it outside up.
    varnished MDF or melamine chipboard forme - oiled.
    it needs vibrating a LOT, and leaving at least a week, or better still a month before demolding.
    if you want to pebble dash it, sprinkle with 10mm pea gravel about an hour after pouring - cover about an inch thick, and brush off the excess when the panel is cured.

    you need to use a greased 8mm rod as a core for the bolt holes - don't try to drill then.
     
  11. bigegg

    bigegg I drink and I know things. Its what I do.

    Messages:
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    Location:
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    I've had a better look at your picture, and it's actually an easier job than I thought - they're basically paving slabs with an edge profile, so:

    cast face down in a melamine chipboard mold, separate strips screwed in to form the profile.

    3:1, chicken wire, vibrated a LOT.
    De-mold after a week.

    25mm bubble wrap might make that texture?
     
  12. julianf

    julianf Member

    Messages:
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    Location:
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    The sections are only 2" (50mm) thick. I was under the impression that steel had to be a minimum of 50mm from the edge on concrete to not rust / blow.

    Even if i managed to get it central, which is pretty unlikley, its only going to be 25mm from the surface - thats IF i manage to get it central!

    The originals have lasted since the 70s with no steel - im wondering if i might not be making more work for myself, and introducing more issues than im solving by putting in steel?
     
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  13. bigegg

    bigegg I drink and I know things. Its what I do.

    Messages:
    4,403
    Location:
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    possibly.
    paving slabs are cast without reinforcing - and they're strong enough.

    it's easy enough to get it centred though, pour half your mix, vibrate, put your mesh in, pour the rest.
    vibrate some more.

    or you can buy little plastic chairs for it to sit on.

    you need a strong concrete mix though - 3:1 minimum
     
  14. julianf

    julianf Member

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    3,236
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    ...and you reckon just sharp sand, no stone?

    Im not against that, but how come no stone?
     
  15. bigegg

    bigegg I drink and I know things. Its what I do.

    Messages:
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    Location:
    Leeds, West Yorkshire
    fault lines: you only need a couple of pebbles too close and near a corner for it to crack off.

    tbh, I was thinking more of the 10mm thick centre infills of "standard" concrete panel.
    I suppose you'd get away with 10mm sharp gravel for this particular design.
     
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  16. colnerov

    colnerov Member

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  17. 500e

    500e Always buy fire insurance, flood are hard to start

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    Go talk to your nearest ready mix about fibers for the amount you need a few beer tokens i would think
     
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  18. knighty Member

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    1,188
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    Sunderland
    I would definitely put stone in, 10mm is normal

    you can get vibrating pokers pretty cheap on ebay....

    or you could could stick a bit of rod into a hammer drill and then go around the outside of the mould with that? (I've never done this... just guessing it's a small enough mould for it to work?)
     
    bigegg likes this.
  19. johnser

    johnser Member

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    1,516
    Location:
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    A thought. How about casting them in situ?

    You've no need for the repeatability and portability casting slabs offers.

    Clamp/through bolt some pallets lined with ply either side of your pillars, reinforce as you see fit, fill and poker a bit.

    Re. Fibres, I bought some for a job I did recently. They go a long way but are a right pain to fluff up and mix in. Would think you'll need a very small amount. I got mine from eBay but if you can find someone locally, as mentioned, for the amount you'd need, could be best.
     
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  20. arther dailey Member

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    2,575
    Location:
    Southampton England
    weldmesh for re enforcement, 5mm would be good .
     
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