Cement residue

[tino8358]

Hey looking for any advice on this really getting the residue cleared up, I pressure washed this already and it has taken some up but isn't looking great

 

[Dave B]

You can wire brush it
There are stone cleaners available but DON’T use brick acid as it will eat at the sandstone and rust any iron in it causing stains

 

[scottish cleaning service]

You would need to go down on your knees and clean with some watered down Phosphoric Acid which breaks down the cement. I usually do it with rubber gloves and a small scouring pad and dip it in the solution and lightly work it in. That's the only thing that breaks down the cement and then you can clean it.

 

[Dave B]

You would need to go down on your knees and clean with some watered down Phosphoric Acid which breaks down the cement. I usually do it with rubber gloves and a small scouring pad and dip it in the solution and lightly work it in. That's the only thing that breaks down the cement and then you can clean it.

I’ll repeat don’t use acid on natural stone especially limestone and sandstone
It dissolves it

 

[K in Kent]

I know some people use brick cleaner (acid) on sandstone, but I completely agree with @Dave B and personally never risk acid on any type of natural stone.
I've tried various 'safe' acid-free products on stone and none of them have worked.
I've also done quite a few brickwork jobs on new buildsand tried multiple brick cleaners. In my opinion the only way to effectively remove cement/mortar staining is with acid. Pressure washing is effective up to a point but you then get the dilema of is more pressure going to damage the surface you're working on?
Bricks and sandstone can only withstand so much pressure before you end up damaging it.
That said, if the stone is in good nick it might be worth trying again with more pressure, but be careful....and whatever you do don't seal it

 

[scottish cleaning service]

Just go into a corner and do a test patch. Quick clean with pad and water down acid then wipe away with a cloth dipped in clean water. No point leaving it looking like that.

 

[Dave B]

If the slabs have any iron in acid will pull it up and rust it
Then another stain to try and remove

 

[Truckcab79]

Just go into a corner and do a test patch. Quick clean with pad and water down acid then wipe away with a cloth dipped in clean water. No point leaving it looking like that.

I lay them and clean them and always use brick acid. Wet it down, work a small area at a time and rinse after. Never had an issue…..yet. ?

 

[scottish cleaning service]

I lay them and clean them and always use brick acid. Wet it down, work a small area at a time and rinse after. Never had an issue…..yet. ?

I'm the same. I think the problem is when one lets it dwell and it gets a chance to eat into the slab. fwiw

 

[K in Kent]

I lay them and clean them and always use brick acid. Wet it down, work a small area at a time and rinse after. Never had an issue…..yet. ?

I know I've seen you post before aying that and if you're confident using brick acid on stone fairplay to you.
I'm sure with the emphasis being on a thorough pre wetting / soaking of stone and a weak dilution? Perhaps several weak treatments rather than anything too strong?

But I think it's also important to differentiate between sandstone and limestone. It may be posoble to safely use brick acid on sandstone but definitely not on limestone.
It is an accepted scientific fact that hydrochloric acid dissolves limestone as @Dave B has already said. This can easily be checked online with all the detail of why this happens

 

[Pjj]

I know I've seen you post before aying that and if you're confident using brick acid on stone fairplay to you.
I'm sure with the emphasis being on a thorough pre wetting / soaking of stone and a weak dilution? Perhaps several weak treatments rather than anything too strong?

But I think it's also important to differentiate between sandstone and limestone. It may be posoble to safely use brick acid on sandstone but definitely not on limestone.
It is an accepted scientific fact that hydrochloric acid dissolves limestone as @Dave B has already said. This can easily be checked online with all the detail of why this happens

Personally wouldn’t want to use it on either once damage is caused it’s difficult and expensive to remedy

 

[K in Kent]

Personally wouldn’t want to use it on either once damage is caused it’s difficult and expensive to remedy

Yeah I agree mate. And it's unforgiving stuff - as soon as it comes into contact it's working and if there's an adverse reaction - too late. Damage is done.

It;'s also worth noting that it should always be rinsed st low pressure using a hose and NOT pressure washed off