Power washing concrete is sometimes all you need to get minor stains off a plain concrete driveway, and it is usually a good way to loosen dirt and extend the life of the concrete. But other times, a strong blast of water may not do the trick, and you need to employ detergents, cleaners and chemicals. Here are the best ways to get several types of stubborn stains off a concrete driveway, thanks in part to the experts at Black and Decker, who wrote "The Complete Guide to Home Masonry."
For a lightly soiled driveway, power washing will do the trick.
Add a Natural Cleaner
Some experts recommend always using soap when power washing concrete. It may not be necessary for simply dislodging dirt, but water alone won’t work on some stains. The most common stain on a driveway is oil that leaked from a car or spilled while doing mechanical work. Water won’t dislodge the oil, and you don't want to spray oily water into the sewer system.
Instead, start by soaking up freshly spilled oil with a commercial oil absorber, cat litter, cornmeal or sawdust. (Dried oil may require more serious cleaners.) After you scoop up and discard the oily material, use the power washer.
Scrub away asphalt, tar, caulk or chewing gum stuck to the concrete with a stiff brush, water and scouring powder. Similarly, soak up any wet paint with rags or paper towels, then scrub the stain with scouring powder.
Quickly soak up freshly spilled oil with an absorbent material to make cleanup easier.
Break out the Chemicals
If none of the above solutions work, try a 5% solution of muriatic acid (industrial-grade hydrochloric acid). It’s nasty stuff, but it will do the trick. Note that it can change the color of the concrete, and might cause burns. Wear protective clothing and eyewear, and protect the lawn and other plants.
Dried oil or gasoline stains can require some specialized alkaline concrete cleaners. Super-Krete is one safe, biodegradable option.
OxiClean and similar oxidizing cleaners are specialized for certain applications and stains. A common example is a protein-dissolving solution that works well on pet urine stains.
Bloodstains may need some powdered sodium peroxide, which is also potentially toxic and dangerous. Again, wear protective clothing. Spray down the powder to keep it from blowing away, then let it soak up the bloodstain, and follow up by power washing the concrete.
Finally, paint stripper works about as well on concrete as on many other surfaces. Soak in some paint thinner on dried paint, then scrub away with scouring powder.
After using chemicals to remove stains, wash down the driveway.
Sometimes your driveway needs more than just a cleaning to keep it looking good. Hire a reliable professional to fill cracks, repair other damage and seal your driveway to extend its life.
Updated January 4, 2018.