Forum: Other Pavings
Topic: Bond bridges, slurry primers for 20mm porcelain
started by: GardenFixer

Posted by GardenFixer on 10 Sep. 2019,13:20
I have received this info which differs from that on this site (namely the addition of water)

"To make a slurry bond the approximate mix is 5 parts Portland cement, 1 part  Prime Bond, 1 part water"

This is for approx 150m of 20mm Porcelain so i'll be working in 25kg, 5kg, 5kg mixes. Any idea how far this is likely to go?

I know it should be mixed to a smooth consistency and then applied to the underside of the porcelain tile using a wide brush until an even coat is achieved, just before placing the tile onto the bedding mortar.

Its a thin contact layer so I'm guessing this will go quite far? sorry if this is a 'How long is a piece of string' type question.....

Posted by Tony McC on 11 Sep. 2019,09:58
I'm struggling with that "recipe". What is a "part"?

Cement is a powder, so measured in kilograms, whereas this Prime Bond is, I assume, a liquid, so measured in litres, as is the water. Given all that, how can a  'part' be defined?

It may well be that, on average, 1 litre of SBR-equivalent will need 5 kg of cement powder to make a suitable paste, and then another litre of water to make it thin enough to work, but it's a bit amateurish to decribe kilograms and litres as being 'parts'. Or do they mean 1 cup of the jollop to 5 cups of cement powder? Your guess is as good as mine.

I'm also wary that many so-called 'primers' are effectively diluted SBR, so there may already be ample water content in this product.

In practice, most experienced contractors wil mix "sufficient" cement powder with a quantity of liquid SBR to make a workable paste. Adding water may well extend the coverage, but it may also compromise the adhesiveness, and I'd only add water is the resulting paste was way to thick to work.

Bear in mind that these self-made primers have a relatively short pot-life - maybe 20 minutes, so don't make too much at once.

Coverage will vary and is largely determined by how generously you coat each paving unit, but, as a very rough guide, a litre of SBR mixed with cement will usually be adequate for around 50m.

Posted by GardenFixer on 11 Sep. 2019,11:35
Its on the basis that generally 1 kg is the equivalent of 1 litre when comparing water volume vs. weight converter.

but that doesn't answer the question regarding mass of the powder.

"Mix to a smooth creamy consistency with ordinary Portland Cement.
The approximate mix is 1 part SBR: 1 part water: 5 parts cement (by volume).
i.e. 25kg cement & 1 tub SBR & water."

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That's the product if this helps a little further.

Posted by Tony McC on 12 Sep. 2019,18:37
If the powder is assumed to be neat (ish) cement, then the density is around 2.4 T/m, almost two-anna-half times the density of water.
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