Fireworks contain sulfur and black powder, and these ingredients can stain surfaces which come in contact with fireworks, such as concrete. These kinds of stains usually happen after celebrations such as Independence Day, where many fireworks are utilized. It may appear difficult to remove fireworks stains from cement, but it is entirely possible to get rid of them and restore the appearance of the concrete walkway.
Mix three parts warm water with one part bleach in a bucket.
Put on latex gloves to protect your skin from the bleach chemicals.
Soak the scrub brush in the bucket with the diluted solution.
Scrub the fireworks stain with the brush in either an up/down or circular motion. Do this for several minutes.
Wash the stains down with a pressure nozzle hose. Flush the stained areas with water until the bleach is removed.
Repeat the steps until the firework stains are removed.
Allow the concrete to air dry for several days.