I often come across concrete like this on older commercial jobs where it looks like an old sealer has become deteriorated and looks like burnt skin is the only way I can think to describe it 
I’ve been cleaning with my standard chems and hot water system and just moving on. Is there a way to actually fix this condition outside of completely removing the old sealer with an acid?
Curious what you guys have done when / if you come across this.
I’m pretty sure that’s the magnesium coming up through the concrete mix, just the way it is. The other guys can comment better than me though.
Funny you posted this one. My own driveway has this problem. 25 years old, never been sealed, surface cleaned 5 times (not by me).
This year I’ve cleaned it twice (18” sc, turned pressure down around 2500 1st time and pre-soaked 30 mins with 3% SH ). Nada?
I even tried an area using OxAcid but it really didn’t do much on the “alligator hide”.
Six weeks later, 2nd time pressure was 3000 and I used 5% SH + Elemonator . Soaked again for 30 mins, only slight improvement.
The “hide” seemed to show up about 3-4 years ago but no idea what caused it.
Others in my neighborhood have the same condition. Btw: it only covers some areas not the entire surface.
Interesting. Yes that’s how it always is when I see it. It’s only in certain areas, not entire slabs. May have to post a question in a concrete subreddit and see if those guys have any answers.
I’ve tried everything I can think of and nothing seems to remedy that “alligator hide” ( I like that description)
Hey Kris!
Yeah, I’m hoping some of the “old timers” here can solve it. Be nice to have my OWN driveway represent that I can get it clean! Lololol
Take care!
Al
I had a driveway do this. Luckily a neighborhood friend of mine works with concrete and mostly does driveways. He described it as a sh*tty poor. DCbrock mentioned magnesium, totally possible. Sometimes companies add magnesium to help against cracking or shrinking, it’s sort of a shortcut. That could be it. It also could have been from moisture that got trapped inside, either from rain, humidity, bull floated at the wrong time, 100 other things he said that I forgot. The ultimate reason was crap poor, I sort of exposed it more by surface cleaning. I have an adjustable gauge on my surface cleaner and I was around 2300 psi. Other driveways in the neighborhood are starting to show the same problem.
Not much to do about it. Repour the driveway, acid etch may help but it depends how deep the problem got “into” the concrete, the best solution if someone really cared would be seal it, my buddy said there’s a way to mimic a cream coat topping but I forgot how, basically a thin layer you pour on top of the driveway.
Either way it’s not something you did. Made me more cautious tho, I start my SC at about 1800 psi and work my way up now, if it’s just surface dirt sometimes you don’t need 2000-2500 psi
