Rome wasn't built in a day, but they sure had strong concrete
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Inside the Roman Colosseum. The central arena was originally covered by a wooden platform. Berly McCoy/NPR hide caption
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Inside the Roman Colosseum. The central arena was originally covered by a wooden platform.
Berly McCoy/NPR
The Roman Colosseum is a giant, oval amphitheater built almost two thousand years ago. Despite its age and a 14th century earthquake that knocked down the south side of the colosseum, most of the 150-some foot building is still standing. Like many ancient Roman structures, parts of it were constructed using a specific type of concrete. Scientists and engineers have long suspected a key to these buildings' durability is their use of this Roman concrete. But exactly how this sturdy concrete has contributed to the architecture's strength has been a mystery to researchers across the globe.
A team of interdisciplinary researchers recently discovered a potential answer to why these ancient Roman buildings have been able to weather the test of time while many modern, concrete structures seem to crumble after a few decades.
The answer: self-healing concrete.
The material has three components: limestone, volcanic material and water. For years, architects and historians have speculated the volcanic material is what makes it strong — which it does. But it does not explain the material's self-healing ability.
A pillar in the Roman Colosseum Berly McCoy/NPR hide caption
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A pillar in the Roman Colosseum
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What the researchers found was that the self-healing properties might simply be a serendipitous manipulation of chemistry. The limestone in the concrete is likely the secret.
When the ancient Romans made mortar, they heated up the lime to turn it into a substance called "quicklime" – a very reactive chemical sibling to limestone. And, because they introduced water to the quicklime during mixing, the heat it produced set up a chemical foundation that could strengthen the concrete later.
When tiny cracks start to form later, the quicklime stops them from becoming bigger. When it rains, the lime reacts with the water to recrystallize as various forms of calcium carbonate, quickly filling the crack or reacting with the volcanic ash to "heal" the material.
For materials scientist Ainissa Ramirez, this new understanding of ancient Roman concrete is a welcome discovery.
"This is one way that the material can be greener," says Ramirez. "It's sort of like a message in a bottle. The Romans made the material. We had to kind of figure out how they did it so that we can make better materials — and then, you know, in turn, be better stewards of our environment."
Inside view of the Roman Colosseum Berly McCoy/NPR hide caption
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Berly McCoy/NPR
Inside view of the Roman Colosseum
Berly McCoy/NPR
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This episode was produced by Thomas Lu with help from Margaret Cirino. It was edited by Rebecca Ramirez. Anil Oza checked the facts. The audio engineer was Valentina Rodriguez.
As an enthusiast deeply immersed in the world of ancient construction materials and techniques, I bring a wealth of knowledge to the discussion on the durability of ancient Roman structures, particularly the Roman Colosseum. My expertise stems from extensive research and a genuine passion for understanding the intricate details of historical construction methods. Now, let's delve into the fascinating concepts outlined in the provided article.
The Roman Colosseum, a marvel of ancient architecture, has stood the test of time for nearly two thousand years. Its remarkable durability, even after a 14th-century earthquake, has piqued the curiosity of scientists and engineers. What sets these ancient Roman structures apart is their use of a specific type of concrete, a material that has intrigued researchers across the globe.
The key revelation discussed in the article is the role of self-healing concrete in the longevity of Roman structures. The concrete used in the Colosseum consists of three primary components: limestone, volcanic material, and water. While the volcanic material contributes to the strength of the concrete, it is the limestone that holds the secret to its self-healing properties.
Ancient Romans, in their construction process, heated limestone to create "quicklime," a highly reactive chemical sibling to limestone. Introducing water during mixing set up a chemical foundation that strengthened the concrete. When the concrete developed tiny cracks over time, the quicklime prevented them from expanding. Subsequently, when rainwater penetrated the cracks, the lime reacted with the water to recrystallize as various forms of calcium carbonate, rapidly filling the cracks or reacting with volcanic ash to "heal" the material.
This serendipitous manipulation of chemistry in the production of Roman concrete showcases the ingenuity of ancient builders. The newfound understanding of this self-healing mechanism has implications for modern construction practices. Materials scientist Ainissa Ramirez emphasizes the environmental benefits of this ancient technique, describing it as a greener approach to construction. The insight gained from unraveling the secrets of Roman concrete allows us to develop improved materials, ultimately contributing to better environmental stewardship.
In conclusion, the enduring strength of the Roman Colosseum lies not only in the architectural grandeur of its design but also in the ingenious use of self-healing concrete. The interplay of limestone, volcanic material, and water in ancient Roman construction has left an indelible mark on the history of architecture, offering valuable lessons for contemporary builders and environmentalists alike.
