Lime or bust lets give the devil his due ; most of us would not be gainfully
employed without the mis use of Portland
Hey...I just merely said I went to a great conference; and its roundheads vs
flat worlds here ....Mike Edison said it best ...very few of us actually work
on anything that was designed for lime mortar and not a complex cement.

stump the chumps .....I will be setting a 80 ft tall monument this summer
that weighs ver 150 tons  each stone weighs over 2 tons ; my joints are 1/2
inch an under closer to 1/4 inch  I want to use a mortar that is high
strength but has good flexibility for thermal movement ........what is your
choose  lime or Portland ???(answer written upside down on bottom of menu)
Now let me make a fool of myself;
Portland,as we know it today wasn't available or did not exist until about
1900 or there after because the invention of the rotary kiln wasn't until
1900.
and as Ralph and Ruth have been trying to tell you it takes very high
temperatures of controlled burning in a rotary kiln to get Portland as we
know it today.
Actually it was the arms race that gave us Portland
British Royal engineers developed it (Vicant 1840-) and they began field
testing with cannon fire directly into granite and brick walls (1870) and
into concrete; Concrete sustained less damage from the new high explosive
shell. Stone and brick were at the height of their craft but the labor was
expensive, after field tests concrete won out and all British forts were
constructed after 1870 in poured concrete. America and Europe followed in the
1890's(Endicott system)These were massive pours in complex lime mortars
topped with Portland to give it strength from incoming shells and to help
water run off .

That is not to say people did not create complex lime mortars that resembled
Portland (fast setting high strength) and went so far to infact call them
Portland
.....in documentation as early as the 1830's.

Now it so happens I am working on a coastal fort that had two periods of
masonry  building 1821-1840 and 1897-02.... I know and have been to where
they made the oystershell lime putty  slaked it with sea water (yes sea water
) worked it with sand ( masons  call it   course stuff) it is covered and
allowed to "cook" under a mound of sand and away from air fro months and even
years.This is carbonate cement
it is used to make pointing material, whitewash . and render .
This same period 1830's calls for by the army corps of engineers to send
complex hydraulic lime mortar(called Portland)  from upstate New York  to be
shipped in barrels alll the way to the Gulf of Mexico    why????
Simply because to set the interior mass of the masonry requires something
that sets by water and not by air ( there is no air in the mass  per se)..
also ..for many practical reasons  such as waterproofing   but the big reason
was setting time and strength  as the lime is slow to set .
One of the tricks of the trade was to gauge ( sprinkle in )  carbonate cement
with hydraulic for setting brick then point up with carbonate the last inch
or so .

Complex lime mortars require controlled burning at lower temperatures than
Portland
(Portland 1200-2000 f)
the limestone for hydraulic lime mortar has clayey bits in it and alumina at
less than 5%; after they are burned they are then  crushed; and mixed with
sand before water is added  but basically its burned limestone with clayin it
 ...Portland is much more complex with alumina iron gypsum and a host of
other impurities that fuse at highr temps .
then comes the different interesting  cements like Roman Natural Pozzolantic
cement  ect  where brick dust is added, different limes  are added together
Bulls blood ect ect fly ash slag ......even dung( as Ralph spoke of )  for
color ....Welll Best of Luck Michael

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