I have had the scalp fungus for 7 years. Told now its caused by the chemicals shampoo manufacturers use.
GP gave me a new one to try. Have tried all the others.
Made it worse than ever.
Then I learned that Cinnamon kills Fungus.
Have been rubbing it into my scalp for 3 weeks, a slow job.
Wash my head every day using toilet soap.
The scalp skin is now peeling away, hopefully taking the
Fungus with it. It has stopped itching. Will continue to wash daily with toilet soap, which doesnt seem to contain the chemical used in commercial shampoos.
Suggest you try Cinnamon on a sample area on your drive
on a dry day.

it could well be lichen. power washing will shift it as will scrubbing with a very stiff brush. a weak bleach solution will also help.

A photo would be helpful, in case you're talking about efflorescence rather than lichen, otherwise, info here regarding cleaning up, but take care which product you use on block paving, a lot of those don't respond too well to chemical cleaners https://www.rhs.org.uk/advice/profile?pid=418

This looks like lichen to me and I'd power wash it if the blocks are suitable for power washing.