What is this?

[socalkol]

So we went to clean some concrete that hadn't been cleaned in years today. Pretreated with sh then surface cleaned. Underneath were these black spots that were not even visible through the grime prior to surface cleaning

Both sh and pressure didn't touch them one bit and they didnt look like motor oil to me.

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[GrassButler]

the bottom pic appears to show them all tract the same way.... i.e. vehicle parked in same spot ( close E-W-N-S ) and the drip runs down.. especially the first 3........ thats my CSI miami observation!!

 

[socalkol]

the bottom pic appears to show them all tract the same way.... i.e. vehicle parked in same spot ( close E-W-N-S ) and the drip runs down.. especially the first 3........ thats my CSI miami observation!!

Thanks Matt, wow I fail i definitely should have noticed that! Guess it could be oil and i just need to train my eyes better.

 

[GrassButler]

IDK.......... just tried to look at it.. it almost looks like tannin staining, except the stains seem to be similarly controlled ( i.e. left from the same object that may sit in the same area or close area very often ) IDK.... you'd think if it were automotive oil there would be spots in-between.... but people can be pretty finicky about where they park and how they line up their parking locators.

 

[Christopher]

Looks like oil or hydraulic fluid stains, will not come out with pressure and SH.

 

[AZ PowerWash Pros]

Maybe date stains? Any trees with dates around? I could DEF be wrong, kinda hard to tell in the pic. But I have had date palm stains that look similar. I use One Restore and they come out pretty well.

 

[Doug Rucker]

Jeff, did you treat it with your SH mix afterwards and leave it??

 

[socalkol]

Jeff, did you treat it with your SH mix afterwards and leave it??

I did doug, praying that when i go back later this weak it is magically gone.

 

[socalkol]

Maybe date stains? Any trees with dates around? I could DEF be wrong, kinda hard to tell in the pic. But I have had date palm stains that look similar. I use One Restore and they come out pretty well.

Thanks Ty, i will have to check the vegetation around.

 

[Doug Rucker]

I did doug, praying that when i go back later this weak it is magically gone.

If it's not oil, and it's tannin from trees, it will be gone in a few minutes with SH. I will sometimes pour a little full strength on it just to see if it does anything. if it doesn't I know I eliminated anything that SH would clean. If it does fade it then I know it's just a matter of the right mix and dwell time.