Pressure washing not removing all of the stains

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  #1  
Old 11-26-18, 03:28 PM
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Pressure washing not removing all of the stains

Hi everyone,

Our driveway and front walkway at our house here in Florida get a lot of what i assume is some sort of mildew over the course of the year. I end up pressure washing it every few years, and i really need to protect it with something to make cleaning easier so i'm not blasting the concrete down to the aggregate, which is the direction i seem to be headed. Before i do that, though, my front walkway has proved especially problematic with these remain black spots. Neither bleach nor vinegar has been able to lift it up. It's definitely not black stone in the concrete.

I'm open to ideas if anyone has any.


Thanks,

Steve
 
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Old 11-26-18, 03:57 PM
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My concrete pool deck gets like that.
I use a revolving turbo tip nozzle but it does erode the concrete every time it's done.
Depot used to carry them. Lowes and Harbor Freight should have them.

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Old 11-26-18, 05:14 PM
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Pressure washer surface cleaner, amazing results!

https://www.doityourself.com/forum/a...1&d=1543281244
 
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Old 11-26-18, 08:54 PM
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What is that DeWalt thing in the photo? Enlarging it just blurs.
 
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Old 11-27-18, 12:15 AM
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Surface cleaner for your pressure washer.

https://www.homedepot.com/p/DEWALT-3...E&gclsrc=aw.ds

My 12 year old paver patio was really dirty as well as the steps. I've cleansed with power washer in the past but it would leave streaks and the patio with all the sand joints didnt seem like it would be a lot of fun.

This think did am amazing job and with no streaking and I actually stayed dry!
 
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Old 11-27-18, 03:48 AM
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If you spray the concrete down with bleach water first it won't take as much pressure washing to get rid of the mildew.
 
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Old 11-27-18, 06:56 AM
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I may not have been clear in my original post about when i applied the bleach and vinegar, but both were applied prior to pressure washing—and not at the same time. Neither made any sort of difference, nor did the "concrete cleaner" that i had purchased from Lowes.

I've thought about trying one of those circular/orbital scrubbers, but haven't really read any great reviews on them. Plus, i've got a lot of concrete to clean and those seem kind of small.

I've had a turbo nozzle before, but it tends to leave the circular patterns too much, which after looking at the Dewalt piece, is a distinct possibility with that as well.
 
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Old 11-27-18, 07:07 AM
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How strong a bleach solution did you use? did you rinse it off before it dried?
 
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Old 11-27-18, 07:10 AM
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I don't quite remember the mixture, but it was the heavy duty clorox concentrate from Home depot. Mixed it as directed. I don't believe i rinsed it off before it dried.
 
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Old 11-27-18, 10:57 AM
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A lot of cleaning agents don't help much if you allow them to dry on the substrate. The cleaner and grime tend to get re stuck. I like to apply the cleaner, let it set but not dry and then pressure wash.
 
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Old 11-27-18, 12:35 PM
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Plus, i've got a lot of concrete to clean and those seem kind of small.
Actually the amount of time it took to do the 24x24 patio and walkway was minimal, much faster than attempting to use any type of hand wand attachment and no swirly marks.

Well worth the $50 investment for the lightly used one off eBay.

Next year it's the entire driveway!
 
  #12  
Old 12-02-18, 09:03 AM
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pres wshing wears out conc - too strong & you'll eat the paste which holds the coarse aggregate together,,, all we ever use is 3,500/4,000 psi w/turbo nozzle HOWEVER that's a prep for applying polymer-modified cementitious overlays & does require a soft touch
IF we just clean, dawn works good as anything else UNLESS you use muriatic acid:water 1:8 mix
 
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