Things You'll Need
Nylon scrub brush
You may only be able to fade the stain. After the stain has faded, the sunlight's ultra-violet (UV) rays will continue to break down the stain over time.
For really deep stains, you can use a concrete etching solution. These products are effective, but they work by actually removing a fine layer of concrete. As a result, they will roughen your concrete and create inconsistencies in the finish. Use these products as a last resort, or if you want to roughen the concrete surface either for added grip or to stain the concrete.
The ingredients in concrete cleaner can burn your skin and damage your eyes. Wear protective clothing, gloves and eyewear when using concrete cleaning products.
Asphalt is some nasty, oily stuff; and if the people applying it aren't careful, it can get onto concrete and create an unsightly, difficult stain. Fortunately, there are some good strong concrete cleaners on the market that can cut the oils in asphalt and lift the discoloration from your concrete walkway or drive. By choosing the right product, and following a few simple steps, you can get rid of those ugly asphalt stains and get your concrete looking good again.
Select a good-quality concrete cleaner. Sodium hydroxide is a strong, effective cleaner that breaks down oil. Oil is one of the key ingredients in asphalt, so what you are looking for in a cleaner is its ability to break down oils.
Mix the cleaner. Concrete cleaning products are generally sold in a concentrated liquid or powder form. Start with a regular-strength dose, but if this turns out to be ineffective, you can mix the cleaning solution stronger until you get the results you are looking for.
Wet the asphalt-stained concrete with water and then apply the cleaner. The concrete cleaner is only effective when it is wet. Wetting the concrete gives it more time to work. If the cleaner begins to dry out, you can mist it with water or add more cleaning solution.
Let the concrete cleaner sit. You can leave the cleaner on for a long while to let it break down those asphalt stains. As long as you keep it wet, it will be actively breaking down the oils in the asphalt. Leave it on initially for an hour; then use your nylon scrub brush to scrub down the concrete and see if the asphalt stain is lifting.
After the oil is lifted and you've scrubbed down the concrete, rinse the area thoroughly with water.
Robert Howard has been writing professionally since 2004 and writes a weekly column for the "Synthesis," a Chico, Calif.-based newspaper. He maintains a blog and has published articles and works of fiction in a variety of different print and online magazines. Howard holds a Bachelor of Arts in visual arts from the University of California, San Diego.