Hi!
I need advice regarding a concrete wall and a concrete staircase we cast outdoors that we plan to plaster this summer. I notice that it's starting to turn green on the concrete (algae, I assume). I think it might be because the sand wasn't sandy enough and soil-like material (organic) has crept into the mix. In any case, the concrete is cast, and it's hardly possible to remove it. The question is how harmful it is? Can I treat the surface in some way before we apply the plaster? Is there a risk that the plaster will fall off or that the green will penetrate through the plaster if it turns out that the concrete is not entirely inorganic?
I need advice regarding a concrete wall and a concrete staircase we cast outdoors that we plan to plaster this summer. I notice that it's starting to turn green on the concrete (algae, I assume). I think it might be because the sand wasn't sandy enough and soil-like material (organic) has crept into the mix. In any case, the concrete is cast, and it's hardly possible to remove it. The question is how harmful it is? Can I treat the surface in some way before we apply the plaster? Is there a risk that the plaster will fall off or that the green will penetrate through the plaster if it turns out that the concrete is not entirely inorganic?
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· Västernorrland
· 12 038 posts
Maybe better to wait with cleaning? Hold off for a year and see how it turns out. It's easy to make hasty decisions before seeing the outcome.
Hmm, true. But it's probably still green in a year, or greener. But maybe that's just on the surface?Stefan1972 said:
Algae grow everywhere - they live on sunlight and whatever happens to be in the air (dust) and rainwater. It probably doesn't have anything to do with the concrete. Wash with high pressure or brush.
Okay! Thanks a lot! Will try that!svartöra said: