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  1. #1
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    Default black mould on exposed aggregate concrete

    Hello All
    For a while(years) I am looking at our black-stained backyard and from time to time, during rain, I also slip on it.
    I've just been looking online and Wet&Forget promises a lot. There is "Rapid Application"(very expensive) and others. What are your experiences with any of these products?
    Have you made a good home brew which also does the job? I'm keen to see what you are using.
    Thanks
    "B.M. The government cannot give to anybody anything that the government does not first take from somebody else": The working class! Let's make sure we vote next time!

  2. #2
    Old guy
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    Default Re: black mould on exposed aggregate concrete

    30 Second Spray and Walk Away does the job. Same chemical as Wet & Forget but about a third the price. Works well but takes a while before you see the results like a couple of weeks or so.

  3. #3
    Senior Member piroska's Avatar
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    Default Re: black mould on exposed aggregate concrete

    https://chemmate.co.nz/blog/post/che...ss-killer.html

    Slow....and chlorine as effective.

    Also, I have found sodium metabisulphite works really well. Husband used to wash his beer kit out with it, and tip it on on the drive...and wow, was it gleaming and white!!
    Ex-pctek

  4. #4
    tweakedgeek tweak'e's Avatar
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    Default Re: black mould on exposed aggregate concrete

    Tweak it till it breaks

  5. #5

    Default Re: black mould on exposed aggregate concrete

    Quote Originally Posted by CliveM View Post
    30 Second Spray and Walk Away does the job. Same chemical as Wet & Forget but about a third the price. Works well but takes a while before you see the results like a couple of weeks or so.
    Quite agree. Wet and Forget is far too expensive. We have used 30 Second Spray and Walk Away as well. Very satisfied even though it does take awhile. We have used it on the black mould on the south side of the house. Recommended.
    It is better to wear out than to rust out.
    - Richard Chamberlain, Tour of the Hebrides

    Us husbands are a sorry lot.

  6. #6
    Can't re Member
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    Default Re: black mould on exposed aggregate concrete

    Wet and Forget you're paying for the chemicals. The rest are no better than Janola and water which is probably fine for concrete

  7. #7
    Older by the minute
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    Default Re: black mould on exposed aggregate concrete

    A Janola & water mix is very effective and quick.

  8. #8
    Old guy
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    Default Re: black mould on exposed aggregate concrete

    Quote Originally Posted by Ofthesea View Post
    Wet and Forget you're paying for the chemicals. The rest are no better than Janola and water which is probably fine for concrete
    30 Second spray & walk away is exactly the same chemical.

  9. #9
    Computer "Specialist" Agent_24's Avatar
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    Default Re: black mould on exposed aggregate concrete

    You may also consider trying muriatic acid to clean your concrete, which can also roughen it, so it should be even less slippery.

    I haven't tried it for concrete myself, I use the acid to make etchant for DIY circuit-boards, although concrete cleaning is one of its advertised uses.

  10. #10
    Senior Member
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    Default Re: black mould on exposed aggregate concrete

    Hi All
    Thanks for all your suggestions, very much appreciated!
    @Agent_24
    It is exposed aggregate, so removing the mould should be sufficient
    @piroska
    I'll going to have a try with
    metabisulphite as I got surplus.

    Spray and walkaway seems to be affordable in case the before mentioned is not satisfactory.
    Once more, thanks!

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