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A couple of weeks ago we had some brick-pavings re-cemented around our driveway. Now all of the grass on the lawn that runs alongside the bricks has gone very orange. I assume it was where the cement/sand mix was brushed onto the grass to clear up after the work.

I read that cement is high in alkaline. Would that have been the cause, and can grass recover naturally or should I purchase some kind of treatment, as opposed to scarifying it out and re-seeding?

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I suggest you wait and see - the other risk with brushing a cement sand mix onto grass is the sand itself might be high in salts, particularly if it wasn't washed sand. If it is a salt problem, that will sit in the soil for a while, possibly some months depending on quantity, until there's been sufficient rain to flush it all away. Given the type of work you've had done though, its unlikely there's a large amount of salt in the soil; even so any attempt at reseeding won't work till the salt's disappeared, so wait and see for a while seems to be the best option. YOu might even find the grass recovers on its own eventually.

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  • Just checking back. "Wait and see" worked out great! The grass is starting to slowly grow back now. I'm going to scarify the dead stuff and reseed. Thank you very much. – EvilDr Nov 11 '14 at 11:48
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I agree that the caustic lime used in masonry is likely the culprit. Depending on how much was washed onto the grass, it could kill the grass, rather than just cause a temporary die-back. However over time it will react with CO2 in the air and turn into calcium carbonate, which is alkaline, but not caustic. A pH test will tell you if you need to make any adjustments. Depending on what kind of grass you have growing, you are looking for soil pH in the 5.0 - 7.0 range.

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  • Great suggestion. I've done this and the 'dead' areas show pH7 to pH7.5, so perhaps slightly biased toward alkaline? Do you think that's worth treating or leaving for the rain to wash through? – EvilDr Sep 19 '14 at 10:48
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    That pH isn't high enough to cause any serious problems - even if it were permanent. Test again in a couple of months. Depending on the area you need to cover and how much you want to spend/risk, you could hedge your bets by seeding and watering the area. Even if the grass survives, overseeding is a nice treat for a lawn. But here's a thought. It just occurred to me that they could have used muriatic acid to clean mortar off bricks - that would certainly cause the burning to the grass that you describe. It would be similar to products like Burnout that use citric acid to kill plants. – That Idiot Sep 19 '14 at 14:30

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