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Stuart Noble

Tim Lamb wrote:
In message .com,
writes
So I can add a few more points to the discussion...

Re adding lime to cement mortars, this doesnt give any of the
properties of a lime mortar. Also most lime/cement mixes are liable to
fail prematurely, so adding a bit of lime to cement mortar or adding a
bit of cement to lime mortar are both not recommended. There has been
research done on this.

Oh.

When this farmhouse was rebuilt, the builders added a couple of shovels
of lime to the mix to *whiten* the end result. The bricks are somewhere
between soft and hard with normal foundations. Ten years on, the mortar
is still sound:-) Not a good match for exposed bits of Victorian stuff
as it is slightly yellow but much better than the khaki colour of my
masonry mix garage.

There is plenty of chalk locally and also grey river clay. I don't know
what the original builders used but it has visible chunks of chalk as
though through improper crushing. The chimney mortar was still soft and
very similar to river clay.

I note that Rugby masonry cement currently contains *fly ash* and that
the concrete floor recommendation included *slag cement* as a retarder.

regards

I thought they still used sugar as a retarder. Jim'll Mix It etc
Anyway, to return to the lime discussion. If the uncarbonated lime in
Durham Cathedral has been protected from carbon dioxide by the
carbonated mortar on the surface, it suggests that lime is capable of
forming an airtight seal, which in turn suggests that the building would
be unable to breathe.....