The Roman Pantheon:
The Triumph of Concrete
An overview of the book by
David Moore, P. E.
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Pantheon
Photo ©1997 Leo C. Curran used by permission
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Revealed within the pages of
this source book is a clear description of the development and usage of
concrete by the Romans in constructing the Pantheon and other still-existent
structures, built around the time of Christ. The book contains architectural
details, sections, pictures, and other features. The concrete dome of the
Pantheon spans some 143 feet without the aid of metal reinforcement like modern
buildings. The building even has unusual cracks and yet it still stands. The
great painter Michelangelo offered one explanation: it is "angelic, and
not of human design." Certainly most if not all of our modern buildings
would not meet the harsh weathering of 1800 years that the Pantheon has endured
and survive. This book answers many of the fundamental questions regarding the
longevity of this beautiful structure and shows how modern concrete
construction is just now learning to apply some of the same technologies used
by the Romans
History and People
There is much more to this
monumental structure, built originally by the Romans as a temple, than first
meets the eye. A shocking discovery is that the building is made of ancient
concrete resting on unstable blue clay. On the surface, at least, this
structure appears to violate all modern building codes and should have fallen
down hundreds of years ago. What is this concrete and how was it molded into
such a beautiful, massive structure?
Pantheon
Photo ©1997 Leo C. Curran used by permission
This book focuses on the
concrete Rome used in many of the structures that are still extant today. The
Romans did not have Portland cement nor concrete mixers, so how did they make
such long lasting concrete? The Pantheon required enlightened technology to
erect a building some 143 feet high using only hand tools. Who were the Roman
engineers? What were their design standards, their instruments, and their
technical education which could make this feat possible?
Lime and Kilns
Lime is one of the first
man-made products relying on chemical reaction - paralleling that of the
manufacturing of ancient clay jars for food storage. The Romans produced lime
by burning limestone pieces in a crude kiln. As a slurry, lime was applied to
protect the earthen walls of ancient houses. When mixed with volcanic ash
(pozzolan) and water, it becomes a mortar that the Romans used to build rock
walls. The Romans later discovered how to mix this mortar with small stones,
bricks, and other materials to produce concrete. Quality control of the
limestone raw material, processing temperature and hydraulic reaction in the
mortar are viewed through the eyes of the Roman. Romans mastered this chemical
processing and manufacturing technology to such an extent that the Pantheon,
which is fundamentally a large concrete structure, is still with us today.
Pantheon
Photo
©1997 Leo C. Curran used by permission
Clay Products
Clay jars, bricks, and tiles
came from the dawn of civilization. The Romans focused on the extensive use of
these products to enhance their lifestyle by constructing magnificent brick and
clay buildings. Strangely, one source of concrete mortar for building Rome came
from a mixture of wet lime and crushed pottery. Vitruvius, a Roman architect,
said this was so. This book verifies his claims by examining the chemistry and
reactions involved in these materials. The ingenious Romans used brick to form
archways over wall openings. It was strong and worked well. Brick also covered
the exterior of buildings.
Identifying Roman Concrete
Scientists have long known
about the components of Roman concrete: wet lime and volcanic ash covering a
layer of small rocks. This is a simple composite concrete. But how did it
become so hard and durable to last 1800 years in the Pantheon? Where was it
found? How was it placed? What did the ancients write about the materials and
processes? These challenging questions are
answered in Roman literature and quoted in the book for the reader. Modern
viewpoints are also included from archaeological studies to bring together this
investigation.
Pozzolan-Lime Behavior
Perhaps the most difficult
part of the research for this book was tying Roman concrete to its modern
counterpart. The explanation includes an examination of the atomic structure,
x-ray analysis, and scientific formulas. Surprisingly, the U.S. Bureau of
Reclamation devised a roller compacted concrete (RCC) that closely resembles
the chemical and material content and manufacturing method used in Roman
concrete 2000 years ago!
RCC is an excellent, durable
concrete of interest to road building engineers and others in the engineering
field.
Pantheon
Photo
©1997 Leo C. Curran used by permission
Ancient Roman Technology
The Romans built many
beautiful, massive structures, unusual for any period in history. Pictures and
sketches of typical buildings are included showing a collective, brilliant
intelligence in action in the ancient world. What was their technology? Who
made up the labor force for this awesome construction feat? What were their
tools and lifting devices as related to our modern types? Fortunately, we have
obtained pictures. Some of these same tools served Christ Jesus in his days as
a carpenter. Some of the topics examined in the book are: metallurgy to make
iron hammers and weapons; material procurement, including shipping; scaffolding
to reach high walls; concrete mortar for construction; construction of
foundations, walls and domes; connecting devices such as wooden pins to make
long bridges possible. By this technology, the famous Pantheon was built to
last the ages.
Reprinted with permission
from the September 2002 issue of
CONSTRUCTOR. In continuous publication since 1919, CONSTRUCTOR is the
national magazine of the Associated General Contractors of America. For more
information, visit AGC on the web at www.agc.org.
