How can I remove dirt stains from concrete driveway?
kyrral
| Posted in Construction Techniques on
I’ve had some flower pots outside for a couple years that I never moved. They have caused circular dirt stains that I can’t remove with a 1400 lb spray washer. There are also irregular low areas that didn’t shed water and are stained. I gues from hard water deposits. Any way to remove these? I tried garage cleaner which I think is formulated for oil/tar that didn’t work. thanks ahead
Replies
Try, separately, muratic (hydrochloric) acid and oxalic acid (often sold as "wood bleach"). (Do not mix the two together!) Muratic acid is good for removing lime (hard water) deposits, while oxalic acid works on rust and some organic stains.
Do NOT use muratic acid on your driveway unless your goal is to destroy it. Muratic acid will etch the concrete leaving it sandy and rough and more prone to staining.
I'd try Outdoor bleach first, Oxy Clean second, oxalic acid third, and phosphoric acid last. Actually phosphoric acid is the best cleaner but will likely be the hardest and most expensive to find so exhaust the other options first. With the bleach and OxyClean time is your friend so let them sit as long as possible. The two acids will work fairly quickly so pour, brush and spray with the pressure cleaner. You might be able to find phosphoric acid in a farm store sold as dairy cleaner.