Is there any natural way to remove lichen from concrete blocks?

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Answered
Hi fellow Hometalkers,

these hexagon concrete blocks are some 15 years old. Is there a natural way to remove those dark stains that look like lichens but have no thickness. Just like they were printed onto the surface. Scrubbing has no effect on those.

- and please ignore the moss on the edges, we've removed that one already :)

Thanks!
q is there any natural way to remove lichen from concrete blocks, concrete masonry
  8 answers
  • Janet Pizaro Janet Pizaro on Feb 20, 2017
    www.ehow.com/how_7678513_remove-black-stains-concrete.html

  • Marlane Rose Marlane Rose on Feb 20, 2017
    We had these spots all over our patio and after trying several proprietary cleaners and a pressure washer (none of which worked) I was thinking of having decking fitted to cover it but after seeing my sister's pristine pool slabs, I decided to try household bleach!
    I brushed thick neat bleach onto dry slabs until it was covered - and left it overnight - it worked. A week later, I had another go to get a better finish but it did not damage the grass or plants although we kept our two little dogs of it. Best of all it was so cheap - we did't use expensive bleach just the supermarkets own brand.

  • Hillela G. Hillela G. on Feb 20, 2017
    Bleach should do the trick!

  • Aun7476306 Aun7476306 on Feb 21, 2017
    I use cheap white vinegar on moss, lichen and weeds on a dry and sunny day. Sometimes takes two applications. It also repels slugs and ants but harmless to pets.

  • Linda Wilmoth Linda Wilmoth on Feb 21, 2017
    We use standard Tide in powder form at home on the cement drive and where I work on the runways at a large condo complex. It works on carpets, tile, stone, and cement. We sprinkle it on during a period of sunny days, it will kill the moss and lichens and in a week then you just sweep it away. No chemicals or hash products to hurt the environment or most importantly your pets and kids.

  • Linda Wilmoth Linda Wilmoth on Feb 21, 2017
    We use standard Tide powder on the runways, cement driveways, tile, and walks where moss or lichens grow. You simply sprinkle it on during sunny weather an sweep off about a week later. It works beautifully with out harming the environment, and most importantly your pets and kids. Easy and not a time intensive process.

  • John John on Feb 22, 2017
    Thanks every one that answered. I use bleach for the green moss, and I was going to suggest boric acid for the spots, but this is a lot safer and cheaper.

  • Mon20899988 Mon20899988 on Feb 23, 2017
    Can vinegar be used on trees & shrubs, to stop it growing and spreading to other plants.