Hi Linda,
Pappy has some good advice as well.
The chems he mentions will work in many situations, however, many local municipalities have begun to take a "california look" at washing chems down the drain and into the water supply.

Not knowing your location, I may suggest that you can use this is part of your marketing .
suggest a solution to a problem!

The problem in this instance is dirty concrete/asphalt right?
The OLD solution was preassure washing ( that may or may not be acceptable in your area)

Jason