Removing mortar residue from paving

[budest]

Hey all,

Looking for some advice regarding removing mortar residue from paving. It was a novice mistake as I'd never laid paving before and having done a reasonable job I then screwed things up with the grouting and failed to wash away the residue. I then tried power hosing and scrubbing each paver and managed to remove the bulk of the mess. It's a base for a shed so I'm not looking it perfect but I'd like to at least try and remove some of the residue to satisfy my OCD.

I'm reading that Muriatic Acid would work. Any suggestions or advice would be welcomed.

Thanks

 

[budest]

Has anyone used this before?

Bostik Cementone Brick & patio cleaner, 5L | DIY at B&Q

Removes mortar stains & limescale

www.diy.com

 

[Mike13]

It works well, but do your best to keep it off the grout lines that you want to keep.
A stainless wire brush to help scrub the stains will help, also hose away well when the sandstone is clean.

i just noticed that those are cement based paving stones, the brick cleaner will attack them also.
I would stick with a good wire brushing

 

[JohnD]

Leave it to fully dry, then walk on it with rubber shoes and it will wear off.

Cement products harden while they are damp, so if you had let the smears dry in the sun, and brushed them away rather than using water, they would have been weak and crumbly.

 

[budest]

It works well, but do your best to keep it off the grout lines that you want to keep.
A stainless wire brush to help scrub the stains will help, also hose away well when the sandstone is clean.

i just noticed that those are cement based paving stones, the brick cleaner will attack them also.
I would stick with a good wire brushing

Thanks for the advice. I scrubbed each stone with a wire brush on Friday and got the worse off (they were far worse) but the residue you see on them now won't come off. I guess with the scrubbing it's forced particles down into the pores of the stone. What I need is something like a liquid to get into the pores and help break it up.

 

[budest]

Leave it to fully dry, then walk on it with rubber shoes and it will wear off.

Cement products harden while they are damp, so if you had let the smears dry in the sun, and brushed them away rather than using water, they would have been weak and crumbly.

Interesting! Thanks for that. When it decides to stop raining here and the stones dry I will give that try.

 

[Mike13]

The "weak and crumbly" phase of cement does not last long, it continues to harden slowly over the first month after mixing, with about 3/4 of the hardening happening in a few days.
Perhaps use a flap disk, with ear defenders and a mask!

 

[JohnD]

Interesting! Thanks for that. When it decides to stop raining here and the stones dry I will give that try.

Too late now. If you can dry it out fast in hot sun, within a few hours of laying, it will be ruined forever and have no strength.

In your case, it would have been deliberate and desired. Usually it is a mistake.

The nominal strength of concrete is achieved after 28 days of continuous damp curing.

With typical rough builders you're lucky if it's kept wet for 7 days (which gives 70% of the 28 day strength)

In fact, it will continue getting harder and stronger indefinitely, provided it is constantly kept wet and never dries out (once it dries, it stops). But the gains get smaller and smaller, and take longer and longer.

If you ever try to break up underground concrete that has been damp for 50 or a hundred years, for example round drains, you will notice it is harder than usual.

 

[budest]

I tried acid cleaner today and whilst it didn't do any noticeable harm to the pavers it didn't help either. It's a case of live with it or lift and replace them.

I laid a mortar base of 6 sand to 1 cement over a hardcore layer of aggregate. I lifted one stone tonight to see if it disturbed the base and it didn't so I either live with the graphite turned greyed stones or lift them and lay new ones.