Knockout

Knockout is a highly effective cleaner for atmospheric and environmental staining, as well as a paint remover. It is a non-flammable and non-acid solution. It works great removing all types of outdoor stains on stone, brick, and concrete, including sidewalks, driveways, pavers and cinderblock. 

In addition to being highly effective, Knockout is super easy to use. Simply apply to affected area, work in lightly, let it set in and rinse off with a garden hose or pressure washer.