Masonry History Integrity - National Center for Preservation ...

Chapter 2: Got Mortar?
What’s Mortar?
Mortar is the material you see in walls
surrounding bricks, blocks or stones. It’s what
holds them together. It looks and feels like
soft mud when it’s being used, but it dries rock
hard and lasts for decades. Mortar has been a
part of masonry construction for tens of
thousands of years, and is not expected to be
replaced any time in the near future.
The word “mortar” comes from the Latin
word mortārium or the Old French word mortier
meaning “something that is crushed or mixed
in a bowl.”
Sometimes mortar is called “cement” but that’s
not 100% correct. Cement is a powder that’s
usually sold in bags and is one of several ingredients used to
make mortar. Think of cement as a bag of flour, the kind used
for baking. Flour is also a powder that’s usually sold in bags. A
cake has flour, eggs, milk and other ingredients. But it’s a
mixture; it’s not just flour. The same holds true in masonry.
Mortar is a mixture of ingredients and not just cement.
Mortar
The word “cement” comes from the Roman word caementum
meaning rough stone and chips of stone.
Portland cement
There are basically three types of mortar that correspond to the
history of the United States from the 17 th century to the present. Each is named for a main
ingredient used in the mixture. They are: Lime mortar, Natural cement mortar and Portland cement
mortar.
Limestone, Quicklime and Lime Mortar
Limestone
Limestone is a common and plentiful type of stone. It
was formed eons ago when layers of decayed sea
animals, mud and shells dried up and solidified.
Limestone is made of calcium carbonate combined
with other minerals and impurities that give it beautiful
texture and variations in color. It’s usually a light tan,
but can vary from off-white to light brown. Besides
being abundant, limestone is fairly durable and easy to
work with. It’s been used as a building material for
thousands of years.
Limestone
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