WEDNESDAY, JULY 3, 2013
The structure of ancient Rome’s concrete marvels is revealing clues to make its modern successors more durable and sustainable, researchers have found.
An international team of geologists and engineers is using the Advanced Light Source at Lawrence Berkeley National Laboratory at the University of California, Berkeley, to describe for the first time how the Romans' calcium-aluminum-silicate-hydrate (C-A-S-H) compound bound the material used to build its long-lasting roads, monuments and harbors.
The discovery of this enduring compound could improve the life span of modern concrete, which often shows signs of degradation within 50 years.
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| D. Bartoli photo, courtesy of J.P. Oleson |
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Samples of ancient Roman concrete were drilled from a breakwater in Pozzouli Bay, near Naples, Italy. The breakwater dates back to about 37 B.C. |
The research team was led by Paulo Monteiro, a UC Berkeley professor of civil and environmental engineering and a faculty scientist at Berkeley Lab; and Marie Jackson, a UC Berkeley research engineer in civil and environmental engineering.
Lifeline of an Empire
Concrete was used during the Roman Empire in monuments such as the Pantheon in Rome, as well as in wharves, breakwaters and other harbor structures.
Particularly interested in how Roman's underwater concrete endured a saltwater environment, the researchers characterized samples of Roman concrete taken from a breakwater in Pozzouli Bay, near Naples, Italy.
"Roman concrete has remained coherent and well-consolidated for 2,000 years in aggressive maritime environments," Jackson, lead author of two papers on the findings, said in a UC Berkeley article.
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| Lawrence Berkeley National Laboratory |
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Roman concrete used a mix of volcanic ash with lime to form mortar, which was then immersed in seawater. Researchers say that producing this concrete leaves a smaller carbon footprint than modern Portland cement. |
"It is one of the most durable construction materials on the planet, and that was no accident. Shipping was the lifeline of political, economic and military stability for the Roman Empire, so constructing harbors that would last was critical," said Jackson.
The ancient concrete combined volcanic ash with lime to form mortar, which was then packed with rock chunks into wooden molds immersed in seawater. The researchers also described aluminum tobermorite—a rare hydrothermal mineral that formed in the concrete.
"Our study provided the first experimental determination of the mechanical properties of the mineral," said Jackson.
Old-World Twist on Modern Concrete
Manufacturing Roman concrete also leaves a smaller carbon footprint than traditional concrete. Portland cement needs fossil fuels to burn calcium carbonate at about 2,642 degrees Fahrenheit, producing seven percent of the global carbon dioxide emissions each year.
Producing the lime for Roman concrete requires a temperature that is only two-thirds of that for Portland cement.
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| Sarah Yang, UC Berkeley |
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Marie Jackson, lead author on two papers about the findings, holds a 2,000-year-old sample of maritime concrete from the first century B.C. |
"It's not that modern concrete isn't good—it's so good we use 19 billion tons of it a year," said Monteiro.
However, Monteiro said it is unlikely that Roman concrete will replace the current version because it is not ideal for fast hardening. But it could lead to the development of more earth-friendly and durable modern concrete, and researchers are studying whether volcanic ash would be a good substitute in countries without easy access to fly ash.
"There is not enough fly ash in this world to replace half of the Portland cement being used," said Monteiro.
"Many countries don't have fly ash, so the idea is to find alternative, local materials that will work, including the kind of volcanic ash that Romans used. Using these alternatives could replace 40 percent of the world's demand for Portland cement," Monteiro explained.
Papers and Funding
Initial funding for the research came from King Abdullah University of Science and Technology in Saudi Arabia (KAUST), which launched a research partnership with UC Berkeley in 2008.
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| Wikimedia Commons / Jean-Pol Grandmont |
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Concrete was used during the Roman Empire in the Pantheon in Rome, as well as in other monuments, wharves, breakwaters and other harbor structures. |
In addition to KAUST, funding from the Loeb Classical Library Foundation, Harvard University and the Department of Energy's Office of Science helped support the research.
Samples were provided by Marie Jackson and the Roman Maritime Concrete Study (ROMACONS), sponsored by CTG Italcementi, a research center based in Bergamo, Italy.
The researchers also used the Berlin Electron Storage Ring Society for Synchrotron Radiation (BESSY) for their analyses.
The findings are described in two papers: “Material and elastic properties of Al-tobermorite in ancient Roman seawater concrete,” by Marie D. Jackson, Juhyuk Moon, Emanuele Gotti, Rae Taylor, Abdul-Hamid Emwas, Cagla Meral, Peter Guttmann, Pierre Levitz, Hans-Rudolf Wenk, and Paulo J. M. Monteiro appeared in the Journal of the American Ceramic Society on May 28 and “Unlocking the secrets of Al-tobermorite in Roman seawater concrete,” by Marie D. Jackson, Sejung Rosie Chae, Sean R. Mulcahy, Cagla Meral, Rae Taylor, Penghui Li, Abdul-Hamid Emwas, Juhyuk Moon, Seyoon Yoon, Gabriele Vola, Hans-Rudolf Wenk, and Paulo J. M. Monteiroscheduled for the October issue of the American Mineralogist.
Tagged categories: Coal ash; Concrete; Life expectancy; Program/Project Management; Research; Salt exposure
