On Thursday, 3 December 2015 10:27:02 UTC+1, Stephen wrote:
Hello,

I read this on the paving expert web site:

"There is often a temptation for installers to use either a mortar
with a higher cement content, say a 3:1 mix in place of a 6:1 mix, to
use PVA as an alleged bonding agent, or to combine a cement-rich
mortar with PVA and hope for the best. Adding cement to a mortar does
not, in very general terms, improve its adhesive properties, and PVA,
being water-soluble, is a sort-term fix that will eventually be washed
away."

It goes on to recommend using SBR. My question is, I have always
followed the instructions on the cement bag, which says to use 5:1 for
general use or 3:1 for a strong mix. The advice above, appears to
contradict that, saying a stronger mix will not actually be stronger.

To put this into context, the paragraph is talking about cementing
pavers as the treads of garden steps. I did use SBR as the web site
recommended, and they do seem rock solid but I was not using a 6:1
mix. Could I have saved cement by doing so? What ratios do you use?


When the instructions say "stronger mix" they mean "higher compressive
strength". They *don't* mean that the concrete sticks more firmly to
an attached brick. (Which is, at least in part, about tensile
strength).