Although water alone can remove dirt from concrete driveways and patio surfaces, cleaning chemicals often are needed to remove specific stains. Use rubber gloves, goggles and keep a hose or bucket handy to rinse it off skin quickly when cleaning with any chemicals. Common Concrete Cleaning Products are kitty litter, water mixed with laundry detergent powder, household bleach, or ammonia. Some brand name cleaners are CLR® bathroom cleaner, Gunk®, STP brake cleaner, Castrol Super Clean ®, Purple Stuff ®, and ZUD ®.
Fresh Stains and kitty litter clay: Your best bet is to clean the stain right away. For fast clean up of liquid stains, clean large amounts of a fresh spill by covering the area with kitty litter. The litter will absorb most of the spilled liquid. If the spill is recent but, has already soaked into the concrete, the litter will draw some of the soaked in liquid out of the surface. Let the litter sit at least 30 minutes before giving up. Be responsible and dispose of the used litter properly; do not wash it down the street into the sewer drain.
Remove Oil and grease with an alkaline degreaser: In addition to hot water, an alkaline degreaser will greatly improve the removal process of oil and grease. Hot water lifts the oil from the concrete, and the degreaser breaks up the oil, allowing it to be flushed from the surface. A mixture of laundry soap, with either bleach or ammonia and TSP can give some results if the stain is not too old. Gunk ® degreaser and Swab, a driveway cleaner product made by Gunk, will minimize the stain but may not clean away a tough stain entirely. Be aware, using a degreaser can leave an undesirable wet looking sheen on the concrete, whereas a commercial driveway cleaner purchased at the home improvement center probably will not. Castrol Super Clean ® and a similar product called Purple Stuff ® is used by many mechanics to clean maintenance garages and tools. A likely place to find Gunk® or Castrol Super Clean ® is an auto parts store. Though soot may not be a problem in all areas, where wild fires leave soot and ash behind, alkaline cleaners are the preferred chemical for cleaning soot from concrete.
Rust: Heavy rust stains can penetrate deeply into concrete, so they can be tough to remove completely. A cleaning product named ZUD contains oxalic acid are most effective as it removes rust stains from most things. Use rubber gloves, goggles and keep a hose or bucket handy to rinse it off skin quickly when cleaning with any acids. Some concrete rust stains can be removed with CLR®, a bathroom rust stain remover. Trying this would be the mildest approach. Start by wetting the area, then sprinkle or spray the stain liberally with ZUD or CLR. Let sit for a few minutes, and then scrub it with a nylon brush (do not use a wire brush). Repeat this several times to remove the rust stain. Unadulterated oxalic acid is often sold as wood bleach, a powder — check the ingredients. Dissolve the powder in warm water until saturated and then brush on the rust stain. Let the remover sit for several minutes. Rinse thoroughly.
Remove Dirt and Mildew Stains with bleach solution: Spray the stain with a solution of one part bleach to two parts water or one part bleach with three parts water. Use rubber gloves, goggles and keep a hose or bucket handy to rinse it off skin quickly when cleaning with any chemicals, even bleach. Let the solution sit on the stained area for several minutes, then scrub and rinse. You can also try laundry powder or dishwashing detergent. Just sprinkle dry detergent on the stain. Let it sit for a few minutes and then scrub with a brush and hot water.
Graffiti: Graffiti can be very difficult to remove, depending on the type of paint used by the graffiti artist. Several citrus-based solvents, methylene chloride, or potassium hydroxide graffiti cleaners are available from the hardware store. Citrus-based solvents are the least aggressive and may not work on certain paints, but they are the safest to use and often have less-stringent disposal requirements. For best results, allow products containing potassium hydroxide to soak into the concrete surface for several hours before power washing. These products also require a subsequent application of an acid neutralizer. Graffiti also can be removed by a special attachment that includes a tungsten-carbide nozzle that meters sand into the water stream before it exits the nozzle. This type of cleaning should only be done by a professional as the sand will etch the concrete, which may not be desirable and can leave you with a bigger mess than you started with. If you have access to a power washer, it’s probably the first thing to try on a stubborn stain (other than fresh oil).
Remove bike tire marks off concrete with Brake Cleaner: Find Brake Cleaner at any auto parts store in many brand names. Spray the brake cleaner on the tire marks. The dark rubber streaks will dissolve and be gone within seconds without even scrubbing!! This can be used on a painted concrete sidewalk; with no damage to the finish. Start trying this as a cleaning agent around the house. It works on wall marks and finger prints too.
Tri-sodium phosphate (TSP) can be purchased a home improvement store or auto parts stores. Dilute one cup of TSP in one gallon of hot water. Pour it on the stain and let it sit for 15-20 minutes. Scrub with a stiff nylon brush. Rinse off with hose and repeat if needed. TSP is also available in a phosphate-free version (which is better for the environment). Always wear eye and skin protection when using cleaning chemicals.
Diluted Hydrochloric Acid: If you have tried all the obvious solutions, and the stain is still there, you may need to try diluted hydrochloric acid, also called muriatic acid. Muriatic acid is not a stain remover or cleaner. The acid actually etches away the concrete itself, and sometimes the stain as well. Use muriatic acid only if you seal the driveway with masonry sealer afterwards. Follow the directions carefully.
Always protect your eyes, face, hands body with rubber gloves and safety goggles when using chemicals of any kind. When diluting acids, pour the acid into water–never pour the water into the acid. Do not get the solution on your skin or in your eyes. Have a garden hose ready to immediately flood any splash areas. Dilute the acid solution first by using a mixture about 4 parts water to 1 part acid. If the stain won’t budge, try a stronger solution until you end up the strength it come out of the bottle. Use a weaker solution first as muriatic acid cleans by etching away the concrete; make sure to rinse it off as soon as the stain is gone.