Bleach's Effects on Concrete

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Bleach is safe to use on concrete.

When applied to concrete, bleach does not harm the sturdy material. However, it does remove spots and unwanted matter from the surface, such as mildew and moss. It also disinfects concrete. When using bleach, work in a well-ventilated area because the fumes from bleach can be overwhelming. Depending on your cleaning project, you might combine the bleach with detergent, dilute it with water or use it straight.


Spot Remover

Bleach serves as an effective spot remover for concrete surfaces. Spray the spot with bleach and let it set for about five minutes before rinsing the area with fresh water. Mixing bleach with ammonia and acidic substance creates a toxic, potentially lethal gas. Therefore, do not clean the spot using bleach if you have spilled other chemicals on the concrete.


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Mildew Remover

Concrete surfaces in damp areas, such as a basement floor, are vulnerable to mold and mildew growth. Cleaning a concrete surface with bleach solution effectively kills the mildew. One such solution includes 1 oz. of laundry soap, 3 oz. of trisodium phosphate, 1 quart of bleach and 4 quarts of water. After applying the solution to the surface, let it stand for about 15 minutes and then rinse off. Always work in a well-ventilated area.



Bleach not mixed with a detergent serves as a disinfectant to sanitize concrete surfaces. Detergents and organic material render bleach ineffective as a disinfectant, according to a report by Cornell University College of Veterinarian Medicine. Therefore, they recommend cleaning the concrete surface with a detergent, then rinsing and drying the area before applying the bleach solution, which should remain on the surface for 10 minutes before rinsing off.


Moss Removal

When applied to moss-covered concrete pavers, liquid bleach removes the moss while cleaning the pavers. Dilute the bleach by adding one part bleach to 10 parts water, and be careful not to get the bleach on nearby plants. While the bleach will not damage the concrete pavers, it can kill your plants, just as it kills the moss.



While bleach will not harm the concrete, it might erode a sealant or paint applied over the concrete. For example, when used to clean concrete tile grout, the bleach can corrode the sealant. Before applying to concrete, consider the effects bleach might have to whatever sealant might be on the concrete surface.



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