Concrete like substance under wheel well

[atlantarange]

Hello All.. I ran over a concrete looking substance on the street the other day and its all over my wheel well. I cant find a hard brush to scrub without scratching the black plastic. Softer brushes dont work. I have tried a number of different cleaners and sprayed with high power pressure wash. I can scrape off with my finger nails but of course its too much underneath for that to be ideal. Any suggestions?

[Don]

Have you thought about using black paint or undercoating to cover it?

[ca.detailchick]

Try using an old credit card and some soap in a spray bottle .If its not too curvy you can use plastic razors.

If that doesnt work try softening it up first with some kind of tire dressing and wait for a few days and try again.

[GettingStarted]

If its concrete try mixing up some sugar water and spraying it onto the concrete.