My local pressure washing distributor and competitor swears by ABR Products (American Building Restoration Products) for concrete cleaning and other applications. I haven't tried them yet, but I might because it is convenient to pick up instead of ordering online.
Rob or Ray, what is your SH to water ratio to clean concrete? I tried in the past to just use SH and water at about a 30/70 mix but had not so good results.
Crisp Cash will usually get a sidewalk the cleanest. SH for a short dwell, then the proper fan tip. Oxalic or Fbarc for rust.
Sodium hydroxide and heat for grease. I'm talking residential. We don't do too much commercial.
After we collect the bags from the gutters from our roof cleaning. .I filter the debri out and x jet it on the driveway. Best chemical ive used. Of course its best cause its free..;-)