Concrete is a porous material. If you have a concrete kitchen floor or countertop, it is sealed so will not easily stain. Concrete on driveways, sidewalks, foundations and sometimes basement floors are not sealed and will easily stain. Most of these stains can be cleaned using products found in your home.
Dirt, Oil, and Grease
Clean your concrete that is stained with dirt, oil and grease with hot water. You can add a small amount of mild dish detergent. If you have a power washer and you can attach it to hot water, that would be best. If not, use a nylon scrubbing brush (not wire) to scrub the area clean.
If grease or oil stains remain, try spraying the area with hot water and then apply the dish soap directly onto the stains. Scrub the area with a nylon scrub brush, working up a good lather. Then soak up the area with a towel or kitty litter to absorb the oil. Then throw away the towel or litter. Rinse the concrete after you have removed as much oil as possible so you don't rinse it into the environment.
If you still have oil or grease stains, purchase an alkaline degreaser or concrete cleaner at your local home improvement store. Follow the application directions on the label; degreasing and concrete cleaners have different strengths.
However, for berry stains, such as cherry or grape, create a thick paste with hydrogen peroxide and flour. Apply it to the stain liberally. Scrub with a nylon scrubbing brush. Cover the area with a piece of plastic wrap and let it sit for one to two days until it dries. Rinse the homemade cleaner away and reapply as necessary.
Use bleach to remove mildew. For concrete outside, use non-chlorine bleach, which is less harmful to the environment. Mix one part bleach to two parts hot water. Use this mixture in a power washer. If you don't have one, use a bucket and scrub brush. Rinse thoroughly.
Rust stains will not be cleaned with a homemade remedy. You will need to purchase a concrete cleaner specifically for rust and follow manufacture directions.