hi john
I clean driveways with a pressure washer.
You don't need any chemicals, just lots of power.
You really need two main lances for you machine too. A fan and a spinner.
The spinner is like a whirlwind that really does clean up drives nicely. then you can wash down with the fan.
You may need a bit of hydrochloric acid to get rid of come cement that have fallen on a driveway. but thats about it really