Cleaning concrete stains
Concrete is highly porous, which means it can stain easily. If left untreated, most stains can move deeper into the concrete, making them more difficult to clean. However, if you identify the stains, act quickly, then use the proper cleaning solution, most stains can be removed. Surprisingly, several common household items are effective stain removers.
Oil Stains
If you have just spilled a container of oil on your concrete floor, do not wipe it up. You'll only succeed in pushing it deeper into the concrete. Instead, grab some cat litter and pour it liberally over the stain, and wait 24 hours. Let the stain soak up into the cat litter so you can just sweep the mess away. If there's any remaining stain, use some scouring powder and scrub it off.
If the stain is older, try using a grease cutting liquid dish cleaner mixed with water. Spread it all over the stain as well as the surrounding areas, and then scrub thoroughly. Make sure you build up a rich lather of soap suds. Be aware that a wire brush can damage the concrete, so use a heavy duty scrub brush instead. Rinse thoroughly when you have finished.
Rust Stains
There are many chemical rust removers on the market, but before trying them, think about a more natural acidic product. Lemon juice and vinegar have both been effective in removing some rust stains. Squeeze a lemon or pour some lemon juice on the stain. Let it stand for a few minutes, then rinse. If there's still some stain left, try doing the same thing with vinegar.
If the stain's still there, it's time to move on to a poultice. Poultices work in two ways in concrete. First the liquid part seeps down into the concrete and breaks up the stain. Then the absorbent portion soaks up the liquid, bringing the stain up with it.
For a rust removing poultice, mix 11 ounces of sodium citrate (available at major drug stores) and 2 quarts of lukewarm water. Add 12 ounces of glycerine. Add a handful of baby powder to the mixture until it forms a thick paste. Let it harden on top of the stain, then scrape it off. Rinse well
Gum
If gum has hardened on the concrete, freeze it by applying ice, then scraping it off. If there's still some left, use some denatured alcohol. Pour it on the stain, and then rinse it off.
Dirt
A mild soap and water solution is usually effective in removing simple soil from concrete, though a little scrubbing might be necessary. When you're using water on the concrete, it's most effective to use a gentle mist-like spray. If the water pressure is too hard, it can push the stain down into the concrete.
Grease
Scrape as much of the grease away as you can, then scrub the remaining stain with scouring powder.
