Robin 58.
What I have been told and have observed is that once the sealer is gone from the concrete its open to the elements. Rain/Snow and freezing/thawing will do the damage over time and the top layer of concrete which doesn't have the rock, because it was 'floated' when finished, will flake off and cracks can happen as moisture penentrates and freezes.
I don't think the pressure washer itself does much if any damage other than removing the protective sealer. The obvious fix is to re-seal after cleaning with a pressure washer.
You probably have less of a problem in the deep South because there is not much freezing.
Jerry
