Hello,
Grateful if a moderator moves this to the correct forum if it's in the wrong place.
During a balcony casting yesterday, it seems the company providing the concrete spilled some on our asphalt driveway. Is there any good/effective way to remove the concrete without damaging the asphalt? We tried rinsing with water when we got home yesterday, but it had already set and cannot be removed even with a brush.
The asphalt is newly laid (6 months) if that makes any difference.
Concrete can be washed away with hydrochloric acid, but I can't guarantee that the asphalt won't be damaged by it, so try applying hydrochloric acid to a corner of the asphalt and see what happens.
Try with a regular hammer. The concrete should be more brittle than the asphalt.
There is a tool called a needle hammer (might be wrong). It is powered by compressed air.
I have used it to remove concrete. It was concrete that had hardened on top of other concrete. So, not on asphalt!
Removing the top layer can surely be done with a scraping tool, something called a coromant scraper. I used it when I scraped casting burrs on newly cast concrete walls and floors. What's run down between the ballast in the asphalt is probably worse. There, it's likely tar or cold asphalt that is needed to "paint over" the concrete that shines brightly.
If it doesn't work mechanically, I would also resort to acid. Hydrochloric acid acts quickly but carries certain risks when working with it, especially so close to a road (eyes, children, dogs, cats, etc.).
Citric acid is available for purchase in larger packages (search for "citric acid 5 kg") and is considerably kinder to work with. Dissolve 5 kg in 3 liters of boiling water (it dissolves faster this way). Pour it over the concrete and cover with plastic. The concrete should be dissolved after a day. Rinse off the citric acid and concrete residue with a pressure washer. Repeat with more citric acid solution if there is concrete left.
