Has anyone seen this before on a concrete driveway?

[Zap It Wash]

So one of my guys cleaned a driveway that's about 1.5 years old the other day and everything went fine. There were some leaf tannin stains at the entrance so he hit those with 12.5 out of a pump sprayer like normal collected a check and hit the road. A few days later the homeowner sent me a picture of these wet-looking spots. This is where the the tannin stains were and he sprayed 12.5. Has anyone ever seen this? I have not.

 

[JBurd]

Is it possible he accidentally used an acid instead of SH and etched the concrete?

 

[814jeffw]

I personally have never seen 12.5% do that to concrete. They look like wet spots. That said,..if they are tannin stains they are easily remedied by oxalic acid @ 6-8 oz. per gallon.

Jeff

 

[814jeffw]

Yes JBurd is correct,..strong hydrochloric (Muriatic) acid will leave the concrete dark.

Jeff

 

[Zap It Wash]

Thanks guys definitely 12.5 truck didn't even have any acid on it. I'm thinking oxalic as well Jeff for touch up and see what happens.

 

[Lightning Gene]

looks like someone tried to clean with too much pressure before on cream concrete to me. Looks like holes in driveway....maybe O tip damage