Removing cement stain from patio

Just had a new buff-coloured patio fitted by a friend. Last thing he said I had to do was to sweep a dry sand/cement mixture over the patio to fill the gaps.
So I mixed two bags of kiln-dried sand with 1/2 size bag of cement and did this. Seemed to fill the gaps OK but now some of the patio slabs seems to have a 'grey' tinge left by the cement.
How do I remove this ? (I've tried both sweeping and hosing).
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The only way to get cement off once it has set is to dissolve it off (other than chipping it off which spoils the surface. You can get cement remover from builders' merchants. It's actual hydrochloric acid. Don't drink it or dip your finger in it.
Rob Graham

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Pressure washer should shift it I would have thought. David
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If theres thick layers of cement try chipping as much off with a chisel etc, then try the pressure washer as much as reasonably possible. If that dosent work you will have to use acid, but be carefull as this may take some of the colour of the slabs in question if you use alot of it!
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If you have a piece of left-over patio slab, use it as a scourer and scrub the stained areas with plenty of water. This will take off the surface layer without introducing any new colouration. I'm assuming that your slabs are coloured right through. Of course you should test this on a small unobtrusive area first. Nick.
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For future reference, what did I do wrong in the first place ???
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Did you make sure that the slabs were *perfectly* dry and the cement/sand was very well mixed. The mixture does sometimes leave a greyish colour(but not as bad as you describe) that is short lived and comes of with a quick hose down.
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Slabs were definitely dry.
Although thinking about it, the mixture possibly wasnt mixed that well.
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cement/sand
colour(but
quick
Try patio cleaner (Thomsons ?). When we had our conservatory built the builders left one of two areas of cement stains on our patio, generally from the holes in the tarpaulin they covered the lawn and patio with. Using the cleaner and a stiff brush bought it up a treat.
Now as for the floor leveling compound their trainee poured, he dropped odd drops everywhere on the patio (and up the house outside walls) and they are still there. They are removed using brick acid, but the acid also attacks the patio so took bloomin ages just dripping on the set blobs of leveling compound.to remove the ones I tried !!!!
To follow the leveling compound story on a bit, after a week drying, large areas lifted up in the conservatory base and cracks appeared. Anyway the trainee lad that did it 1. Didn't sweep the concrete base before pouring leaving the leveling to set over piles of dust. 2 Didn't PVA to it so it didn't even stick on the non dusty areas. Anyway the builders came back and lifted the compound up in huge sheets except for where he had poured it our where it had actually bonded to the floor.
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1.Better to vacuum the floor to get rid of the dust 2.The primer should be just to seal the porous substrate rather than as an adhesive, pre wetting should be all that's required
--
David

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from
Spookily enough just bought some of the Thomsons stuff. Yet to try it though...
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Paul W wrote:

When you've done it, can you post the results and method used under this thread. Got the same problem :)
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