How Does Oil and Grease Stain Concrete?

Porous Material

Oil and grease (and other liquids) stain concrete because concrete is actually a porous material. It has tiny holes in it which allows liquid to pool and soak deep into the concrete. Once spilled, grease and oil stains should be cleaned up quickly, before they have a chance to penetrate deeper into the concrete. The reason old grease and oil stains are more difficult to clean up is because they have penetrated very deeply into the concrete. In addition, grease and oil do not dissolve in water, so it is not easy to clean them off of concrete with soap and water.

Other materials spilled on concrete, such as some paints or food, are somewhat easier to clean because they are water soluble.

Absorbing

Although concrete does absorb liquids quickly, it is possible to get the stains out, especially if they are fresh. The first step in cleaning up a grease or oil spill from concrete is to blot absorb it with paper towels or any other absorbent paper. If you try to rub at the stain, it will only push the liquid deeper into the pores of the concrete.

Next, spread a layer of cat litter, sawdust, corn meal, or any other absorbent powder onto the spill and let it sit overnight. The powder will work to draw the grease or oil up out of the pores in the concrete and into the material. In the morning, wipe up the absorbent powder.

Scrubbing

After you have absorbed as much of the grease and oil as you can, the final step is to go ahead and scrub the concrete as hard as you can. Scrubbing with a stiff brush will allow you to reach down into the tiny holes in the concrete and remove the grease or oil. Scrubbing alone, however, is not very effective. You will also need to use a cleaning solvent. Trisodium Phosphate mixed with bleach to form a thick paste is very effective on oil and grease stains on concrete, but be sure to use it in a well-ventilated area, and protect your skin with heavy rubber gloves. You can buy Trisodium Phosphate at any home and garden center.

If you don't want to use a chemical solution, you can also try a pressure washer to blast the stains right out of the concrete. While this does work, it can also damage your concrete. Use it only after you've tested it, or if you really don't care if you pockmark the concrete.