Michael Edison <[log in to unmask]> wrote:
> It may be somewhat out of the mainstream, but I tend
> to think the moosh phenomenon is actually one of the
> beneficial properties of lime. Dry it out and it
> un-mooshes.

One of my projects at present is an 1880s brick
warehouse / bond store located about 150m from a
relatively sheltered salt-water harbour wharf.

The mortar joints which we believe to be a lime & sand
mortar, are in the following condition:

1) Very thin, say 1-2mm (1/16"), crust of harder
mortar which, when undisturbed, can be broken with a
pocketknife.

2) Behind this, the mortar has begun to disaggregate
into sand - you can scrape it out as loose grains -
don't know what it is like when wet - we looked at it
in the dry, thank goodness. Question is whether this
dry moosh is adequate - Answer is not once the crust
is gone.

3) Eroded in some areas up to 50-75% of the thickness
of the bricks (and yes, some of the bricks are falling
out).

We're proposing to repoint with a lime-based mortar,
because some of the bricks are also beginning to
decay, and we do not want to accelerate their erosion
by repointing.  Our starting point was a simple 3:1
sand/lime mortar, but I know it is not as simple as
that.  Or is it as I used to think ... all in the
curing?

Parameters it seems I need to consider:

1) Constituents
2) Proportions (ratio)
3) Grain-size distribution
4) Nature and condition of lime (slaked lime, lime
putty, hydraulic lime ...)
5) Method of curing

Workshop task for the Pinheads ... suggestions please
(and it will be interesting to see how many
conflicting opinions we can accumulate and force me to
test my powers of judgement on!!!!!).

Cheers
david



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