Okey Dokey,
Layman off the starboard bow.....  Can you explain to me the difference
between pozzolana, volcanic ash, volcanic tuff and volcanic rock?  Mike,
John? (Oh, and welcome to BP fellow lurker.)
Best,
Leland

Leland R. S. Torrence
Leland Torrence Enterprises and the Guild
17 Vernon Court, Woodbridge, CT  06525
Office:  203-397-8505
Fax:  203-389-7516
Mobile:  203-981-4004
E-mail:  [log in to unmask]
www.LelandTorrenceEnterprises.com
 

-----Original Message-----
From: The listserv that doubts.
[mailto:[log in to unmask]] On Behalf Of John Walsh
Sent: Monday, November 12, 2007 6:36 PM
To: [log in to unmask]
Subject: Re: [BP] Ganita in the 5th

Okay, I've been silently stalking this forum for several months now and I
guess 
it's about time I pipe in and introduce myself.  John Walsh here and some of

you may have met me in San Juan or sat in for my presentation Monday 
morning with Dorothy Krotzer.

I have to agree with you Mike.  Natural cement (the American variety) was 
exceptionally common down south in the latter half of the 19th century.  I
find 
it regularly in Florida, Geogia, and the Carolinas.  Much of Rosendale
cement 
was shipped widely and of course Louisville cements representing the second 
largest cement producing region in the country (available in the 1830's) and

Georgia cements (available by 1850) were used regularly.  Add to this the
St. 
James cements and extensive Potomac valley manufactories and there should 
be no doubt that the cements were available.  And yes, stuccoes were 
another popular application of the cement that I find pretty often.  In
fact, 
Dorothy and I presented last week on natural cement stuccoes that we 
identified at the College of Charleston ca. 1851.

But as a materials scientist, I have to take exception with your
classification 
of natural cement as a pozzolan.  Pozzolans are any type of reactive
silicate 
(usually glassy or poorly crystalline) that require lime to be activated.
The 
reaction is caclium hydroxide (from the lime) with the base-soluble silica
(from 
the pozzolan) producing caclium-silicate-hydrates, essentially the same 
primary binder material created through the hydration of most cements 
(natural or otherwise).  

Natural cements are true hydaulic cements meaning they react readily with 
water to produce the binder (of course, I know you know this so forgive 
me...this bit is more for any casual reader).  As such, they require no lime

addition to do what they do.  In fact, I very rarely find any lime at all
added 
to natural cement mortars in the U.S..  Unlike portland cement (which never 
was really formulated for useful masonry properties and hence is a 
compromise), natural cements tend not to require the "sweetening" properties

of lime.  As you've said, elasticity is different in addition to other
properties.  
Shrinkage is different as well which is why I usually find natural cement 
mortars surviving quite happily with narrowly graded and rounded sands with
a 
sand to binder ratio of 1.5 to 1.  Try that with a straight portland.

Anyway, I have to get back to writing reports so that I can enjoy some 
stuffing (with Italian sausage as the aggregate of course) next week.

John Walsh

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