The Brew Cabin

Posted: **Sat Jan 18, 2014 8:00 pm**

Cobble project still ongoing. Pointing using a gun. Didn't add SBR to pointing mix (3/1 sand/cement), that's in area that won't be waked on.

From pavement to front door I laid marble slabs with a few cobbles mixed through to help it blend together. I gave slabs a 12mm joint using tuck pointer so joint should be consistent. I have a small bit SBR left over and thought of adding it to pointing mix in path that will see foot traffic.

I gave all cobble bases a dip in SBR paste and it was blue//grey ish, would pointing mix go that colour, and would finished result stay that colour or would it end up same colour as 3/1 mix?

As always thanks for help and advice, it's been greatly appreciated.

Posted: **Sat Jan 18, 2014 9:41 pm**

i would be very wary using sbr in a pointing mix. because it is a bonding agent it will significantly increase the chance of staining your slabs with a few spilt drops or excess mortar.

SBR can be horrific to try and shift and gives everything that blue haze. In fairness the small quantity you would use in a pointing mix shouldn't make it obvious its more the staining potential.

Others may have different views though as its not something i have done, above is just my gut feeling

Posted: **Tue Jan 21, 2014 11:18 am**

You're right about the potential to stain if it's not cleaned off *immediately* with water and a sponge or cloth, but for all of the mortars I've worked with over the years, I've never known SBR affect the cured colour.

Admittedly, I've not worked with every local sand, but certainly all the usual suspects from Northern England maintain their colour when beefed up with the SBR.

That bluey-greyey-lilac colouring disappears as the SBR cures. If you let a small puddle of it form on a plastic sheet and let it cure for a few days, you end up with a transparent splodge. Here's some on a piece of Brazilian dark slate after 24 hrs.....

The Brew Cabin

Does sbr change colour of pointing mix