From the Hoover Dam and the Burj Khalifa to the Panama Canal, concrete underlies the greatest of modern architectural achievements. But modern concrete, it seems, doesn’t hold a candle to Ancient Rome’s.
A little history for you: the Romans were the first to engineer concrete in mass, and it was upon this concrete that they built their empire. After the Empire fell, though, the knowledge of concrete construction went with it. Concrete gradually came back over the following centuries, but did not return to form until a version of producing modern concrete, called Portland cement, was developed in 1824. There was only one problem: it wasn’t nearly as good as the ancient way.
As the many tourists of Italy have recognized, the Roman structures have stood the test of time. Particularly noteworthy for engineers, geologists, and architects are Roman-era harbors. Roman concrete harbors, despite spending 2,000 years awash in the waters of the Mediterranean, are still around. Aqueducts might deal with small levels of erosion, but harbors surviving for two millennia of constant bombardment is a marvel—Portland cement would only last 50 years before eroding. Befuddled, researchers from Italy and the U.S. took to analyzing samples from 11 Roman-built harbors.
Businessweek has more on the developments:
The findings, which were published earlier this month in the Journal of the American Ceramic Society and American Mineralogist, are considered so important for today’s industrial engineers and the future of the world’s cities and ports. “The building industry has been searching for a way to make more durable concretes,” [research engineer Marie] Jackson points out.
Another remarkable quality of Roman concrete is that its production was exceptionally green, a far cry from modern techniques. “It’s not that modern concrete isn’t good—it’s so good we use 19 billion tons of it a year,” says Paulo Monteiro, a research collaborator and professor of civil and environmental engineering at the University of California, Berkeley. “The problem is that manufacturing Portland cement accounts for 7 percent of the carbon dioxide that industry puts into the air.”
The secret to Roman concrete lies in its unique mineral formulation and production technique. As the researchers explain in a press release outlining their findings, “The Romans made concrete by mixing lime and volcanic rock. For underwater structures, lime and volcanic ash were mixed to form mortar, and this mortar and volcanic tuff were packed into wooden forms. The seawater instantly triggered a hot chemical reaction. The lime was hydrated—incorporating water molecules into its structure—and reacted with the ash to cement the whole mixture together.”
What this means for modern architecture is possibly revolutionary. We’ve known for some time that volcanic ash was important, but the research has revealed a better understanding of the composition of this spectacular Roman concrete. Of course, translating the principles to modern construction is an entirely different problem to tackle. But it could result in a more durable and, importantly, greener buildings for our contemporary empires.
Below, a little bit on “How Concrete is Made” from ConcreteNetwork.Net. They know what they’re talking about.
“Ancient Roman Concrete Is About to Revolutionize Modern Architecture” by Bernhard Warner, Businessweek