re: Borrowed a $1500 pressure washer from a neighbor..OMG

Even the 3500 psi units are pretty good at blasting away the cementitious concrete cream on the surface and leaving the aggregate exposed. It depends on the psi of the concrete, how it was poured, what tip you use, and how close you place the tip to the surface.

I can't tell you how many times we have had a goofball masonry laborer screw up a brick wall with a pressure washer.

Cleaning is great, creating a partially exposed aggregate finish is not good.