Concrete Worktops / Polished concrete Tables

Discussion in 'Other Trades Talk' started by Haybarn_on_the_hill, Aug 10, 2020.

  1. Haybarn_on_the_hill

    Haybarn_on_the_hill New Member

    Hi all!

    I'm looking to create either a smooth concrete worktop, or table and wanted some advice on the concrete mix....
    There is a stack of advice in the USA about products, but most of them aren't available here.

    So, I need a nice strong concrete mix that's going to give me a really smooth finish without any gravel showing through, but i'm unsure as to the quantities of everything I need.

    I'm thinking of:
    - Standard Cement
    - Builders Sand (not sharp sand)
    - 10mm Gravel aggregate
    - Plasticiser
    - Wire mesh

    ....If anyone has better ideas, let me know!!

    Has anyone on here made any nice concrete tables before? If so could you give me some advice on mixes/products?

    Thanks in Advance!
     
  2. Dan Parkinson

    Dan Parkinson Active Member

    I can't help you but I am thinking of doing something similar. Interested to know why you're using building sand? I had thought about granno to dust as my sole aggregate. Don't think I'd bother with plasticiser either.
     
  3. Drewton

    Drewton Member

    I can't give much advice but it all sounds about right what you've listed. Also I hope you share some pics of the end result!
     
  4. Haybarn_on_the_hill

    Haybarn_on_the_hill New Member

    I was thinking of the plasticiser so I can add less water, keeping the concrete as strong as possible...
     
  5. rogerk101

    rogerk101 Screwfix Select

    Plasticiser won't make it any stronger, but it would make it slightly more workable. However, it's not really a situation where workability is an issue ... you're going to be working it pretty well to get it as dense as possible anyway.
    I would make it in two layers, with one cast just before the other. The mix for the bottom layer contains a few fistfuls of glass fibres (the ones specially designed for concrete mixes), and makes up 90% of the thickness. The mix for the second layer is without glass fibres, and makes up the remaining 10% of the thickness. The reason for this is that the glass fibres will add whatever tensile strength would normally be provided by rebar/steel mesh, but you don't want that visible in the final top surface; hence the two layers.
    What ratios will you be using?
     
  6. Haybarn_on_the_hill

    Haybarn_on_the_hill New Member

    Chers - yeah, i'm leaning more towards a glass fibre mix now for sure.
    i'm not sure on ratios - its so hard to get advice on the perfect mix and wehat should actually go into the concrete...any tips on the mix to use?
     
  7. rogerk101

    rogerk101 Screwfix Select

    I'm assuming you don't want your top to be much thicker than 40mm, ideally even thinner; so you'll need it to be really strong, but not too strong that it risks cracking with the slightest movement. I would have thought about 4:1 should do it, but what do the USA sites say? Will you be using grey or white cement? I think the white would look better, but I don't know if it is as strong as a premium grey cement. It would be worth checking.
    Do you plan on polishing it? How do you plan on treating/sealing it?
     
  8. stevie22

    stevie22 Screwfix Select

    Plasticiser will cut down the water required to get the required workability. Reduced water/cement ratio means better strength and reduces the risk of bleeding.. Follow advice on tin though!

    I like the 2 layer idea (the top needs to go on immediately) and I think I'd go for grano. Make sure your forms are not going to stick to the concrete (oil or polythene) and cure it very carefully for several days.
     
  9. Haybarn_on_the_hill

    Haybarn_on_the_hill New Member

    Do you reckon grano will give a decent result? Would you then not use any sand and just a 4:1 grano/cement ratio?
     
  10. Riddor

    Riddor Member

    put a poker on it to get a good finish on the sides
     
  11. Haybarn_on_the_hill

    Haybarn_on_the_hill New Member

    A poker?
     
  12. Riddor

    Riddor Member

    Vibrating poker lay it flat a small one works a treat
     
  13. Mick_austin

    Mick_austin New Member

    Hi how did the worktop go? How has it lasted and what ratio did end up using?
    I’m trying to get hold of 40n premix bags but they are like gold dust at the mo, so I’m going to have to mix my own, I just can’t find any strength additives to strengthen up the normal Portland cement.
     

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