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For Concrete That Lasts, Do as the Romans Did, Berkeley Scientists Find

Berkeley scientists studying concrete that is strong and intact after 2,000 years submerged in seawater on the coast of Italy say the ancient Romans have lessons to teach us about making concrete more durable and environmentally friendly.

Marie Jackson, member of a research team headed by UC Berkeley engineer Paulo Monteiro that studied ancient Roman concrete, holds a sample similar to the material that was tested. Photo Credit: Sarah Yang, UC Berkeley
Marie Jackson, member of a research team headed by UC Berkeley engineer Paulo Monteiro that studied ancient Roman concrete, holds a sample similar to the material that was tested. Photo Credit: Sarah Yang, UC Berkeley
Tests on ancient underwater Roman concrete by scientists from Berkeley and elsewhere may have found ways to make our buildings and bridges stronger and longer-lasting. 

When Julius Caesar, Nero and other Roman emperors wanted a break from their empire-ruling duties in Rome, they'd find respite in magnificent villas at the ancient port resort near modern Naples called "Baiae," said to have been named after Ulysses's helmsman, Baios, in memory of the epic wanderer's supposed visit to the area.

It was there that Hadrian breathed his last and where scientists recently retrieved some of the remarkably long-lasting concrete that has endured intact under seawater for two millennia. (Part of Baiae was built underwater as port infrastructure and part was later submerged by the region's volcanic activity – Pompeii-burying Vesuvius is nearby.)

The study "described for the first time how the extraordinarily stable compound – calcium-aluminum-silicate-hydrate (C-A-S-H) – binds the material used to build some of the most enduring structures in Western civilization," said a UC Berkeley news release.

The tests not only revealed the secrets of the ancient concrete's durability but also showed that the ingredients are those that can be produced with less damage to the environment than is caused today, according to a news release from the Lawrence Berkeley National Laboratory, where some of the tests were conducted.

The analyses "pinpointed why the best Roman concrete was superior to most modern concrete in durability, why its manufacture was less environmentally damaging – and how these improvements could be adopted in the modern world," the lab said. 

We know the general recipe of lime and volcanic rock for Roman concrete from writers like Pliny the Elder, who died in the eruption that buried Pompeii. An international research team – headed by UC Berkeley civil and environmental engineering professor Paulo Monteiro – identified secrets of the Roman cement, the "glue" that holds concrete together.

Much of today's concrete is made with Portland cement, which requires greenhouse-producing high temperatures to produce. The tests of the Roman concrete showed that its ingredients can be "made at two-thirds or less the temperature required by Portland cement," according to the Berkeley lab.

Among the important differences of the Roman cement is added aluminum and less silicon, the lab said.

The analyses also found that the world's abundant supply of aluminum-rich volcanic ash, pozzolan, could be tapped as a substitute ingredient.

“For us, pozzolan is important for its practical applications,” Monteiro was quoted as saying. “It could replace 40 percent of the world’s demand for Portland cement."

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