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In article ,
(N. Thornton) writes:
(Andrew Gabriel) wrote in message ...

strength of a stronger mix. And I believe the lime content has limited
crack healing ability.

Lime acts as a plasticiser and makes the mix easier to handle.
I doubt if you are going to get much in the way of tollerance
to movement unless you take the cement out. I also use a
waterproofer (actually combined waterproofer and plasticiser,
so I end up with a lovely creamy/smooth mix to handle).

In lime mortar, lime reacts with CO2 to grow a crystal across the
crack, and this self healing provides some movement tolerance. I'm not
sure if there may still be a bit of this action with a lime cement
mix, but the lime can still meet the CO2, as the plaster would crack
at the same time, so it seems quite likely, unless perhaps you know
about all this in greater depth.

No, and I've found it pretty impossible to get definative info.

However, a lime mortar is flexible, so in the event of movement,
you get many smaller-than-hairline cracks which are self-healing
as you say -- lime is exposed and reacts with CO2 to make more
chalk, which is what the lime becomes when it sets. However,
1:1:6 is not flexible to the same degree, and you will get fewer
larger visible hairline cracks, which the lime isn't going to be
able to do much about. I think the significant things about the
1:1:6 mix is it's not so strong that in the face of movement it
makes the bricks crack, and it doesn't take the days/weeks a
lime render takes to go off -- you can skim it after 24 hours.

--
Andrew Gabriel