Concrete stained from sprinklers

5 years ago

Hi. I had my house completed about 1 year ago in June. We immediately had our sprinklers and sod installed so we could start getting our yard established before it got too hot. We were told we should seal our concrete when we can, but at that point the temperatures were already in the low 90s consistently and the products I had found said they should only be used when temperatures are consistently below 85. We decided to put it off until fall.

Unfortunately, we found that within just a month, our concrete was being stained where the sprinklers overshot the yard and created a nice dark strip on either side of the driveway (our water is quite hard, if that matters). I was hoping that with time, the water would work its way out and it would return to its normal color, but one year later it is still stained. We did not end up sealing in the fall to try and give it time to even out with the winter snows, but that didn't work.

Is there anything we can do to try and remove or even out the stain apart from trying to wastefully run water over the unstained parts of our driveway? It's not the end of the world, but it definitely detracts from the look of the concrete.

Thanks

Featured Answer

Dan

5 years ago

Talk to your concrete installer and see if they have any recommendations.

You can also try using a very dilute mixture of oxalic acid. Make sure you take every precaution. Rubber gloves, goggles, a respirator (not just the surgical style mask) and a long handled scrub brush.

Wet the concrete down a bit to prevent it from drying out and then apply the oxalic acid/water mixture and scrub, scrub, scrub. Keep dunking the brush into the mixture. Let it soak, but don't let it dry. And then rinse it well. You can up the concentration of oxalic acid if you need to speed up the process, but no more than the recommended amount.

Oxalic acid is the bitter substance in Rhubarb and that is why you should never cook rhubarb in anything but a stainless steel pan.

It is also the active ingredient in ZUD cleanser.

Good look, and have fun. I am an experienced DIYer and managed the paint desk at several of the orange big box stores so I do have knowledge in this area. But, as I suggested, ask your concrete install what they suggest as they should know of what they talk about.

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Comments (9)

c0demancer
Original Author
5 years ago
Thank you for the response. That's an interesting idea. I always assumed that the stain was deep in the concrete. I will see if I can track down the installer (or find an alternate contractor if I can't) and see what they recommend. If all else fails I can test the oxalic acid on a small piece.
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PRO
Yardvaark
5 years ago
We're depending on your analysis of the stains cause being accurate, but there's not a great way to gauge if this is correct. Could you show a picture that captures the condition as good as possible?
c0demancer thanked Yardvaark
c0demancer
Original Author
5 years ago
Yes of course. Thanks for the response. Here’s a picture.
PRO
Yardvaark
5 years ago
I'm educated-guessing because I don't know the history, but it has the look, to me, of having had a surface curing compound applied to it. Then the sprinklers quickly washed away the fresh compound at the edges, leaving concrete without curing compound, at which point, it began its natural aging process ... just what you'd expect it to do. The rest of the driveway (the white part) was longer protected (possibly even still is protected) by the compound so it's aging process has been delayed. I speculate that after a couple of years of aging, the white portion will catch up to the so-called stained portion. If this was my driveway I would do exactly nothing but let weather and time work on it. I don't think I've ever seen concrete with any age to speak of that still had a pronounced white portion on it. It's only a year old so there is lots of hope to be had by doing nothing.
c0demancer thanked Yardvaark
PRO
Yardvaark
5 years ago
Here is some general info copied about curing agents...

DO make the process easier by applying a curing compound.

If other methods are not feasible, there’s a simpler solution yet: curing compounds. Available from DIY stores and ready-mix concrete companies, these contain soluble emulsions that form a protective film when sprayed directly onto the surface of newly poured concrete slabs or walls. Ultimately, the film provides a barrier or film to prevent water from evaporating, allowing it to cure at a consistent rate. Some curing compounds are designed to disintegrate completely after a couple of weeks, while others should be removed by scrubbing after the curing process is complete. Still others, such as Quikrete Acrylic Concrete Cure & Seal, penetrate the surface of the concrete, becoming a permanent sealer that waterproofs the concrete to keep it looking freshly poured. Read the manufacturer’s labels carefully before choosing a curing compound to ensure that it meets your specific needs.
c0demancer
Original Author
5 years ago
Thank you again for your response. I had wondered myself if it would even out over time. I’m happy to wait it out rather than take drastic action.
Dan
5 years ago
I agree, leave the concrete alone. From the initial comment, I thought it was much worse. Save the oxalic acid trick for more severe stains that other cleaning methods can't touch.
PRO
Yardvaark
5 years ago
FYI, the reason I asked for the picture is because there are certain unusual components of fertilizer (I forget now what but think it might be manganese) that will stain concrete literally black. While the stain lasts for a LONG time (more than a year) it will eventually fade, too. I thought, since the stain was near the drive edge, it might be that. But in the picture, it's clearly not.