1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Concrete and cement questions

Discussion in 'Building' started by securitynewbie, 24 Nov 2017.

  1. securitynewbie

    securitynewbie

    Joined:
    22 May 2016
    Messages:
    89
    Thanks Received:
    1
    Country:
    United Kingdom
    Hi guys. I have a question (or two).

    Our drainage pipe was damaged, so we had to get a trench dug up. I've fell out with the guys who did the job.

    Anyway to cut a long story short I've been left with a hole. Not only that, but they also took out what looked like a mixture of solids and clay from under the drain pipe with an SDS drill chisel, so it has little support.

    1. What is the mixture of solids and clay and how do I fill under the drainage pipe to support it again?

    2. The original surface was concreted, so I'd like to replace this:
    a) What materials do I need to make concrete?
    b) Can I use rapid set cement as part of concrete material?
    c) I plan to work on the weekend which cold/frosty. Is it worth adding something into the concrete mix to help it cure?

    Thanks for your help.
     
  2. Sponsored Links
  3. Paulg31

    Paulg31

    Joined:
    26 Mar 2008
    Messages:
    107
    Thanks Received:
    8
    Location:
    Warwickshire
    Country:
    United Kingdom
    I’d use something like 10 mm pea gravel to bed the pipe. This should support the pipe and then be back filled to surround it. You can then use your soil above it.

    I’d be carful concreting in frosty weather. The general rule is don’t concrete unless it is 3C or rising. You’ll need to insulate it if it’s colder overnight.
     
  4. securitynewbie

    securitynewbie

    Joined:
    22 May 2016
    Messages:
    89
    Thanks Received:
    1
    Country:
    United Kingdom
    Cheers Paul.

    The pipe is hanging almost midair with nothing underneath it, so how can I put 10mm gravel under it?

    Regarding the concrete. It's going to be around 5C-7C during day and around 2-3C at night. This is why I'm thinking to use rapid set cement and some sort of frost protection.
     
  5. John D v2.0

    John D v2.0

    Joined:
    26 Aug 2016
    Messages:
    6,315
    Thanks Received:
    876
    Country:
    United Kingdom
    If it's above freezing the concrete won't freeze. Even below freezing it's rare the frost gets very deep into the ground. Cement It generates a bit a self heat when curing too. You can always use warm water and cover it if you're worried.
     
  6. securitynewbie

    securitynewbie

    Joined:
    22 May 2016
    Messages:
    89
    Thanks Received:
    1
    Country:
    United Kingdom
    Thanks John, that's very helpful.

    This brings me on to my other questions:

    1. Can I use rapid set cement to make the concrete?

    2. Is it worth purchasing a 5l frost protection chemical to add into concrete or is that not needed?

    3. What is the mixture of solids and clay and how do I fill under the drainage pipe to support it again?
     
  7. noseall

    noseall

    Joined:
    2 Feb 2006
    Messages:
    38,793
    Thanks Received:
    2,477
    Location:
    Staffordshire
    Country:
    United Kingdom
    Unless the pipe is in a location that requires unusual support, just fill it entirely with pea gravel.
     
  8. Sponsored Links
  9. securitynewbie

    securitynewbie

    Joined:
    22 May 2016
    Messages:
    89
    Thanks Received:
    1
    Country:
    United Kingdom
    Cheers noseall. The garden is normally used for parking vehicles and the pipe is below.. I need to make sure that the ground is solid enough to drive over. Since the pipe is hanging almost midair, will filling pea shingles under it be strong enough?

    Also any help on my other questions would be very much appreciated.

    Thanks
     
  10. noseall

    noseall

    Joined:
    2 Feb 2006
    Messages:
    38,793
    Thanks Received:
    2,477
    Location:
    Staffordshire
    Country:
    United Kingdom
    For vehicular traffic - no. Just bang some concrete in there but support the pipe (usually with a brick) as you do. Then chuck some material on top to stop jack getting at the cement.
     
  11. Ian H

    Ian H

    Joined:
    14 Sep 2010
    Messages:
    6,442
    Thanks Received:
    739
    Location:
    Rochdale
    Country:
    United Kingdom
    I would just use pea gravel. Once it's in you can stand on the pipe and it won't move, once backfilled and reinstated you can drive over it.

    The pea gravel is free flowing so just pour it in then knock it under the pipe with the blade of you spade.

    You can use rapid set if you know you will have it done fairly quick.
     
  12. tomfe

    tomfe

    Joined:
    27 Aug 2014
    Messages:
    1,262
    Thanks Received:
    160
    Country:
    United Kingdom
    Depending how deep the pipe is just pea in the hole will do.
    If you do will with concrete I'd wrap some polystyrene around it so any movement won't crack the pipe.
     
  13. John D v2.0

    John D v2.0

    Joined:
    26 Aug 2016
    Messages:
    6,315
    Thanks Received:
    876
    Country:
    United Kingdom
    Just for clarity, the OP isn't actually s suggesting to concrete the whole hole, if you read the actually questions the concrete is only the top layer.
    Having said that my concern would be cracking of the concrete where the backfill settles. So maybe the pea gravel only then concrete would be better?
     
  14. securitynewbie

    securitynewbie

    Joined:
    22 May 2016
    Messages:
    89
    Thanks Received:
    1
    Country:
    United Kingdom
    Cheers everyone for your help. I already have lots of pea shingle (10mm??) left over from a previous job, so I guess I could use that?

    John is correct in saying that I'm not looking to concrete the whole hole, just the top few inches.

    Correct me if I'm wrong, but can the following method work? :-

    • Fill the lowest drop of the hole with a 5-6 inches layer of loose ballast and lightly mixed concrete
    • Fill the remaining hole with clay/soil upto the bottom of the drain pipe
    • However when I get to the drain pipe, I fill under that with pea gravel.
    • Then the rest of the hole with more clay and soil.
    • The final layer is then concreted

    Here is a picture to better explain:

     
    Last edited: 25 Nov 2017
  15. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page