What is the easiest way to get concrete off patio slabs

[Maggie1]

My son recently rendered my walls and there are patches of concrete on the slabs (and in between some) Some of the concrete has been there since last year when the wall was built. I am now cleaning the slabs with a pressure washer which is getting up some of the concrete, but some has gone rock hard and I have been scraping it which is really hard. Is there something I can do to make this task easier.
Thanks

 

[PrenticeBoyofDerry]

what are the slabs made of, sometimes using brick or a diluted hydrochloric acid can soften concrete snots and lumps.
But beware on some materials it can have an adverse effect, as it can burn in to cement based surface and leave etching.

 

[Maggie1]

Hii, thanks for replying, am not sure to be honest, they are the type you get at B&Q the coloured ones not the grey street type. I have some patio cleaner is this the kind of thing u mean? sorry to sound so dumb .

 

[noseall]

You waited a year to clean em off!!

Had you cleaned the muck off when the plaster was applied it would have washed off a doddle.

A week later and it would have been a bit more stubborn.

After a month you would have had a fight.

A year on... no chance. You will need to physically remove any large chunks with a hammer and bolster. Hydrochloric acid is only good for smears or stains. It would take several applications to wear down anything thicker than a mill' or two.

 

[PrenticeBoyofDerry]

Hii, thanks for replying, am not sure to be honest, they are the type you get at B&Q the coloured ones not the grey street type. I have some patio cleaner is this the kind of thing u mean? sorry to sound so dumb .

Likely to be wet cast concrete then, acid will burn them, you'll end up having to go over the whole lot to make them look the the same.
Patio Clean what does it say it does?
and what's in it.
Sound like you need elbow grease, hammer, chisel and a stiff brush and a stiff drink!

 

[Maggie1]

Hi
Several hours, many blisters, severe backache and a lump just below my thumb joint (where I hit it with the hammer) later. I have done just what u said and it is now not too bad. It's not my fault I'm just the little woman clearing up after the lazy men who didn't bother to hose the slabs down when they finished lol.
Many thanks for your help though, just having the stiff drink u mentioned.
Cheers
Maggie