The right type of concrete

Discussion in 'Builders' Talk' started by Laurent VIDAL, Sep 22, 2021.

  1. Laurent VIDAL

    Laurent VIDAL New Member

    Hi concrete experts!
    I am re-building the stairs outside to get to the house.
    I have build a wooden frame to poor the concrete in and added 12mm rebars.
    Now, I called a local concrete company "Aire concrete" to poor the concrete for me.
    They are asking me what type of concrete do I want?
    I have no idea... They sugested ST1 or ST2 is it a good choice?
    What would you use? What the standard for outdoor stairs ?

    Thank you,
  2. Severntrent

    Severntrent Screwfix Select

    What are the rebars doing, neither of those mixes are structural. I assume they are going to be mass concrete stairs?
  3. Laurent VIDAL

    Laurent VIDAL New Member

    Hi Severntrent,
    What do you mean by "mass concrete stairs" ?
    They are poored in the wooden frame straight onto the ground on a bed of gravels. Not suspended or anything like that.
    I am an engineer I can deal with mechanical, electrical... but when it comes to concrete I don't know much really...

    Stairs are 5m long 12 steps + a landing of 1.2m on the top.
    What type of concrete would you use?

    Thank you,
  4. Severntrent

    Severntrent Screwfix Select

  5. stevie22

    stevie22 Screwfix Select

    What are you looking at? Steps or stairs as they are very diferent.

    If it's just a couple of steps sitting on the ground then ST2 will be fine but as Severntrent says the rebar won't do anything. If on the other hand its stairs which means effectively a beam then it's a whole different ballgame and the steel needs to be designed and a structural mix giving a specified minimum strength used
  6. Laurent VIDAL

    Laurent VIDAL New Member

    Hi Stevie,
    I mean stairs. 12 steps + landing.

    Well, all the steps are linked together by the concrete (about 54cm / 21 inches thick) but I did not dig out the soil for the entire staire case if you see what I mean ?
    I put steel bars in it as per various youtube videos...
    So, is ST4 the right stuff ?

    It would be so much easier if I could upload a picture... :)

    Thank you,
    Last edited: Sep 22, 2021
  7. Severntrent

    Severntrent Screwfix Select

    Screenshot_20210922-165426.png So something like this formed on sloping ground with a wooden frame and then infilled with concrete?
  8. Laurent VIDAL

    Laurent VIDAL New Member

    Yes, something like that . just the concrete is thicker, and it is suported by the ground, not floating.
    What type of concrete would you use for that ?

  9. stevie22

    stevie22 Screwfix Select

    Unless you know how to build just about the most tricky type of formwork going, then I'm afraid you're doomed to failure.
  10. PhilSo

    PhilSo Screwfix Select

    But true...

    Post a pic of the formwork/shuttering please.

    PhilSo (Curious)
  11. Severntrent

    Severntrent Screwfix Select

    I would go with ST4 for durability reasons.
    Laurent VIDAL likes this.
  12. Laurent VIDAL

    Laurent VIDAL New Member

    Hi Severntrent,
    Thank you very much!

    I'd love to mate... Just don't know how... It seems on this forum you can only post a pic if it is already uploaded on the web somewhere.

  13. Laurent VIDAL

    Laurent VIDAL New Member

    Hi Severntrent,
    What is the difference between ST2 and ST4 ?
    I mean what makes the ST4 so much strongger? More cement? Less water in it?
  14. Severntrent

    Severntrent Screwfix Select

    More cement, same ratio of water to cement,
  15. Laurent VIDAL

    Laurent VIDAL New Member

    Thank you very much. ST4 ordered. ;-)
  16. GRH

    GRH Member

    I'm intrigued, please let us know what happens (all good I hope), but anyway this is a page turner.

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