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.

What happens if you leave bleach on concrete?

A simple solution of household bleach poured onto the problem area followed by a hot water rinse can remove dirt, grime, mold, and mildew. In certain instances, using a scrubber or a broom with a bleach solution can release embedded dirt. Since concrete is porous, it will retain both odors and stains.

Will bleach turn concrete white?

Bleach is commonly used to whiten concrete and is very effective at doing so if the initial stain is removed beforehand. Bleaching stained concrete white prepares it for any additional coloring treatments that you may wish to apply in the future.