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Reply To: | BP - Dwell time 5 minutes. |
Date: | Fri, 20 Nov 1998 01:25:44 -0500 |
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Ken Follett asked "Why is that?" (Limestone instead of lime in masonry
cement)
I haven't found the answer yet, but thought sharing my research so far might
generate an answer from others.
I have checked various texts on masonry, cements, stone, lime, clay and find
no mention of "Masonry Cement" in books dated 1905, 1918, and 1931. Masonry
Cement does not appear in the 1906 Sweets Catalog (reprint). I t does not
appear inthe 1931 Graphic Standards (reprint). The first reference I find
to masonry cement is found in a 1946 US publication "Brick Structures."
PATENT or MASONRY MORTARS.- A number of brick mortars and trade-marked
brick cements are now on the market. Some consist of portland cement, lime
and sand mized dry and sold in bags. Others consist of natural cement mixed
with hydrated lime or portland cement; and some also contain water-repellent
materials, such as oils or soaps.
Note that this reference does not mention crushed limestone.
John Ashurst in Volume 3 of his 5-book series mentions "Modern Cements" and
includes masory mortar (without mentioning contents) but states that these
cements have various additives that improve workability or water-proffing
qualities.
From the research I have developed a theory which I'd like to test against
all you BeePers. Limestone often contains magnesia and clay, both products
that are constituents of natural hydraulic cements. After WWII the Portland
Cement industry pretty much took over the concrete business, leaving one or
two struggling producers of hydraulic cement (prime among them Century or
Rosendale Cement.) I propose that crushed limestone may have been added to
Portland Cement in an effort to provide some hydraulic cement
characteristics derived from the added magnesia and clay. This would have
occurred after WWII when the supply of natural hydraulic cement was drying
up, and the Portland Cement industry was competing for market share.
Further research avenues might include patent records, publications of the
Portland Cement Institute, advertisements in architecture/construction
magazines from the 1930s-1950s, or maybe ask an old mason. Is this a thesis
topic for some nascent academician or newly minted-diploma holding
"expert"??
Just some thoughts.
Michael
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