I own a 3200 2.8 gpm machine. Today I tried to wash my concrete for the first time.
I used a 10% Sodium Hypochlorite solution (Walmart Pool Essentials Chlorinating Liquid) with a downstream injector, that allegedly pulls 10:1. I applied the mixture to my side walk with the soap nozzle. I allowed the SH to sit there for 20 minutes. I then proceeded to clean the sidewalk with my 15 inch two nozzle surface cleaner. I saw the dirt and algae come right off, did two passes. Rinsed all dirt off and then did a post treatment with the SH again for 10 minutes, then rinsed it off.
I let the sidewalk dry completely and IT IS CLEANER but it is not lighter in color. I did a test, put the 10% SH full strength in a little spot. It took 42 minutes for it to dry up and it actually stained the concrete but did not remove the dark spots. I then pressured washed the little spot with my 15% nozzle (which doesn’t damage my concrete). I was surprised to see that the concrete still wasn’t any whiter in that area!!!
What in the world? Do you think it is my 8 year old concrete or do you recommend using a different chemical? Straight water does not brighten my concrete.
How can I brighten my concrete by 3 or 4 shades? I’ve noticed that the concrete that is semi protected by the overhang looks nice and bright. However, the unprotected concrete has thousands of dark rocky/pebble looking spots on it. My driveway is made out of the same concrete but I figured I would start learning with the sidewalk.
How can I make the dark spots go away?
