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The Roman Pantheon: The Triumph of Concrete

An overview of the book by
David Moore, P. E.

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? 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.

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.

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. 

Copyright © 1999 David Moore, PE