Yellow looking driveway?

[KDJ]

Cleaned a driveway the other day, (first one) Then the next day I drove by to see my great job I did, and it just looked yellow to me. The driveway has most likely never been cleaned (PW) before, there was heavy mold, rust and oil spots. I knew the rust and oil spots would still be there but never thought the driveway would turn from black to yellow!
I applyed Sodium Hydroxide to the surface, gave about a 10 min dwell time then started to wash. The cleaner was working well (I think) as the black mold was turning a brown/orange looking color and I was getting what I would call a mud type affect. I rinsed the driveway real good , then put a light coat of chorine and left it to dry. Chorine was applied downstream at about 10 to 1 (pool grade) Need some input here

Thank You

 

[doug mckenzie]

if there is iron in their water ,this may be the cause when you did the last step. i think someone has said oxyalic acid works. suds

 

[MR ALAN]

"I rinsed the driveway real good , then put a light coat of chorine and left it to dry"
I do not use chlorine, so I may be off a little, but it seems like you would have to rinse it and not let it stay there and dry. Since yellow is the color of the chlorine, maybe all you have to do is rinse it again, very well.

 

[doug mckenzie]

it's not left over chlorine. suds

 

[Clean County]

If the driveway was black before it was cleaned due to years of dirt/mold build up on it among other things, all of this this might have discolored the concrete a little bit.

For this driveway to be black in the first place sounds like the homeowner probably never had it cleaned or waited along time between cleanings. Either way I'm sure he was happy because it looks like night and day compared the way it looked.

So my guess is that the Concrete was discolored due to the neglect in the homeowners part and if he is not complaining then don't worry about it. I bet he was happy when he saw it after you cleaned it.

Time to go to the next job.

 

[ron]

i think

you should have brightened it with oxalic acid. I use this on most homeowner flatwork. Also it may have taken out some of the rust stains.