Andrew Gabriel wrote:
The Natural Philosopher writes:
I found that the lime addition - which I really did to get
a color and texture - seemd to make the mortar stickier.

Yes, but not once it's set. The lime eventaully becomes chalk,
which is not known for its tensile strength.

Mortar or concrete in general are not known for tensile strength!

I do use lime in
mortar for work in lime mortar buildings, but that's precisely
because you don't want the mortar firmly bonded to the bricks.
I wouldn't use it where you want the mortar to glue something in
place, like the top exposed layer of a wall.

1:1:6 is still pretty tough stuff compared to plain lime
mortar. If you want to stick the cappings down a cement/PVA
slurry brushed on before they are bedded will make them
stay put quite unnecessarily well. Simply soaking the
surfaces is probably enough - I'd personally rather that
any stress from movement is released through the mortar,
rather than the sandstone.

For the colour effect alone, you can buy white cement.

Yup, that's good for effect when (say) grouting paving
flags/slabs, but not for (say) pointing lime-mortared
brickwork. Presumably that's why you say "colour effect
only" above!.


J.B.