Concrete cured with dark blotches
by
Brian
Had concrete poured in November and there are still some large, dark blotches on it. Need options for fixing them.
My concrete problem - walkway
My concrete problem - sitting area
My concrete problem - closeup. Notice the scratches on the dark area that show light greyy underneath, almost like the dark part is just on the surface.
Another closeup
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Just to wrap up: Turned out this was "retained moisture" caused by "hard troweling" where they trowled the surface a little too late, after it had already started to set up. This causes the top surface to "densify" which prevents all the moisture from leaving during the curing process. The solution was to wet the concrete with water, then apply an even layer of white vinegar, and leave it sit in the sun all day. The acid in the vinegar opens up the pores in the concrete surface and allows the trapped moisture to evaporate. I repeated this process 3 times and all the dark grey areas are gone now! Thanks everyone for your help.
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I have the same problem, but this is in a poured basement. Will the vinegar still work with no sun?
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