What can I use to clean my cement driveway that appears to have a dark mold on it?
It even becomes a little slippery when it rains. There was a very large oak tree on the side of the driveway that I had removed close to a year ago. I thought that maybe shade from the tree may have helped in causing it. Would appreciate any help.

Bleach will likely work.

KISS is certainly correct about bleach killing mold. However, I suspect that the tree might have been dripping sap which makes things a bit stickier (couldn'tpass up the chance) Test a spot with bleach but also test a spot with TSP or other strong dtergent, wear gloves and googles with TSP. A pressure washer is also a good approach to use on concrete.

There is an insect called Aphids that suck the plant juices from the leaves of Oak trees and excrete a substance called honeydew. It might be this on your driveway. Mineral sprits will take it off if TSP, as Ballenger suggested, doesn't work.

I found something that says black sooty mold sometimes forms on honeydew. It says to remove it with a wax and grease-removing product or rubbing alcohol.

I agree but since this is concrete we can get a little aggressive and the pressure washer with detergent should blast this junk away.

I agree, pressure washer is the way to go. Where's that person starting up a drive-way pressure washing business?

Good one amricca, I totally forgot about that guy. Bet I can dig him up.
Thanks,Bob