Removing excess mortar from paving slabs

declanafc · 10 Apr 2009

Am new to all this, so everything is a steep learning curve, from building retaining walls to fencing, my rear garden is very steep, so have had to cut out 4 levels and make retaining walls, steps etc, all good fun but have slightly mucked up with paving.

I decided to to lay the paving on concrete as the ground was very unstable, so i used hardcore then a 2" bed of concrete, that went well, time will tell.
Anyway i used mortar to to fill the gaps, on day one went well but the second day i was rushed, left without cleaning the excess no i have a framework of excess mortar on some of the slabs, tried using a wire brush but will take forever and i fear damage to the slabs, any ideas, i would prefer not use chemicals, would a pressure washer work, any ideas please??

Thermo · 10 Apr 2009

what sort of paving is it?

declanafc · 10 Apr 2009

Here is a pic, cant remember name of the slabs, i still have the last row to lay at the back between wall and patio but weather has intervened, though would like its all cleaned up before i do.

http://i84.photobucket.com/albums/k3/declanafc/IMG_0477.jpg

Thermo · 10 Apr 2009

in the word of the bard, they are well and truely ****ed up. youd be better swapping them for fresh ones for the wasted time effort and expense in cleaning them. pressure washer, brick acid etc etc wont shift that

declanafc · 10 Apr 2009

Unfortunately i am stuck with these, cost and time being the reason, and they are all concreted in, lifting them isnt a option, i need to find some way to clean them, albeit a wire brush, as i have had luck with that, just wondered if there was a quicker method

declanafc · 10 Apr 2009

Worse case i will have to cover paint, thats the worse case scenario

Symptoms · 10 Apr 2009

dec - I share Thermo's reservations but if you can't (don't want to ) lift them try some brick cleaner (mortar cleaner) carefully brushed on the offending bits; you might just be lucky in loosening it. Have plenty of water handy to neutralise the acid.

declanafc · 10 Apr 2009

If finance wasnt a issue i would, plus they are imbedded now in the concrete, i would loathe to paint, i will try and use a wire brush and slowly remove it, worse scenario perhaps coloured mortar

BUT say i cant remove and i need to make good without replacing the slabs

Whats my best options??

Symptoms · 10 Apr 2009

try the brick cleaner ... you never know!

stuart45 · 10 Apr 2009

The brick acids that you get now are quite weak, but you can increase the strength by adding some spirits of salts crystals.

WabbitPoo · 11 Apr 2009

stuart45 said:
The brick acids that you get now are quite weak, but you can increase the strength by adding some spirits of salts crystals.

Couldn't agree less. Get some from a builder's merchants and its strong stuff. So much so that it hurts on the skin. You'll need to water it down before using it, cos your slabs, also cement-based, will be affected too. Brush on, leave for a bit, then attack with a brush.

Good luck. Gonna need it. Someone post this post as a sticky - perhaps in DIY Disasters!

stuart45 · 11 Apr 2009

They will still hurt your skin slightly, but they are still much weaker than you used to get. I agree that a strong acid could damage the slabs which won't happen with bricks, so you need to make sure that you brush it on to the stains only.
If you can get some crystals you won't need to buy acid from the merchant as its the hydrochloric acid in it that reacts with the cement. You just need to add some to water.

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Removing excess mortar from paving slabs

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