Thanks for the responses so far, but it seams to me, clumping issues aside,
that PCL makes a much better mortar - better plastic deformation and
autogeneous healing of cracks. What purpose does the pulverized limestone
have (powdered aggregate?) and isn't hydrated lime better?

Also the technical notes from the Brick Institute of America and the
Portland Cement Association "qualify" the heck out of describing what
masonry cement is - there is no good info provided. The primary aspects
mentioned are job site ease - one bag for cement, a pile of sand and water.
How is one supposed to confidently specify mortar when you can't find out
what is in it?

Mike E, can you shed some of your wisdom?

Thanks,

Eric Hammarberg
Director of Preservation
Associate
LZA Technology
641 Avenue of the Americas
New York, NY 10011-2014
Telephone: 917.661.8160 (Direct)
Mobile: 917.439.3537
Fax: 917.661.8161 (Direct)
email:  [log in to unmask]



-----Original Message-----
From: S. Stokowski [mailto:[log in to unmask]]
Sent: Tuesday, February 04, 2003 10:52 PM
To: [log in to unmask]
Subject: Re: Masonry Cement or PCL


Eric:

Masonry cement is a mixture of Portland cement, mineral filler, and other
components.  The mineral filler is usually limestone powder.  It can be
other things, such as diatomaceous earth, ground basalt, ground feldspar,
ground quartz, etc.  The "other components" that I allude to, if included,
are usually hydrated lime, an air-entraining agent, and in some situations
an anti-cake agent.  Calcined bentonite and calcined kaolin clays have also
been used.  During the manufacture of masonry cement the Portland cement and
the limestone powder are usually mixed and interground in a ball mill.  The
Portland cement becomes finer, more reactive, and more effective.  Limestone
is the usual mineral filler because it does not cause excessive wear on the
ball mill.  The approximate proportions for Type N masonry cement are 45%
Portland cement, 45% pulverized limestone, and 10% hydrated lime.  In
manufacturing practice, the proportions are adjusted to a happy medium
between workability, ASTM C-270 strength, and RMC (raw materials cost).

It has not been my experience that the manufacturers will not divulge the
composition of their product.  However, the sales force usually does not
have this information in their memory, although if you read the MSDS you can
get a good qualitative idea.  The MSDS usually doesn't tell you the
admixtures, but they really aren't that difficult to identify with $10 worth
of labor and $20,000 worth of knowledge.  The quantitative proportions are
usually only known to the lab and production guys.  And to guys like me who
reverse engineer and develop these products.

Masonry cement is on the market because it is a profitable product that
performs well.  It is primarily a bagged product.  As such, it has a major
advantage over bagged Portland cement/hydrated lime mixtures; it cakes less.
That is primarily because of the interground mineral filler.  Masonry cement
is also less expensive and has a couple of purely technical advantages.  If
an air entrainer is used, the resulting mortar has enhanced frost
resistance.  If the mineral filler is limestone, the masonry-cement mortar
also has more acid resistance because of the reactivity of the pulverized
limestone with acids.  There are also more nebulous advantages related to
masonry cement being a relatively "Green" product.

Steve Stokowski
Stone Products Consultants
Building Products Microscopy
10 Clark St., Ste. A
Ashland, Mass. 01721-2145
508-881-6364 (ph. & fax)
http://members.aol.com/crushstone/petro.htm
<http://members.aol.com/crushstone/petro.htm>

******************************************************
In a message dated 2/4/03 4:41:31 PM Eastern Standard Time,
[log in to unmask] writes:



I am trying to find out why masonry cement (MC) is on the market when
portland cement / lime (PCL) mortars appear, at least to me, to perform
better and more reliably?

As many of us know, MC is typically a mix of portland cement, pulverized
limestone and "proprietary admixtures" which manufacturers seldom (never)
will divulge. PCL is portland cement and lime, period.

Can anybody shed light on this for me?








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