Secrets of Roman Concrete Probed to Develop More Sustainable Modern Varieties

The concrete used by ancient Romans to build structures that have withstood the elements for thousands of years is being given a fresh look by scientists who hope to better understand the key to making more durable and sustainable concrete.

A team at University of California, Berkeley conducted an analysis of Roman concrete and discovered the simple material was able to stay held together for so long because of an extraordinarily stable compound - calcium-aluminum-silicate-hydrate - that binds the material.

The find may play a role in developing better formulas for modern concrete.

While concrete is one of the most commonly used building materials in the world, its role in creating carbon emissions is significant and overlooked. Each year about 19 billion pounds of concrete are used around the world, and the high temperatures necessary to produce it are responsible for as much as seven percent of all human carbon dioxide emissions, UC Berkeley reports.

But Roman concrete is much cleaner, requiring temperatures two thirds of what's required to make modern concrete. It is also is known to withstand submersion significantly longer than modern concrete.

"Roman concrete has remained coherent and well-consolidated for 2,000 years in aggressive maritime environments," said Marie Jackson, lead researcher. "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."

Paulo Monteiro, a researcher at the U.S. Department of Energy's Lawrence Berkeley National Laboratory, told U.S. News & World Report that "We have to find alternative ways to make concrete."

"It's a beautiful material, it's used all over the world, but the weakness is we use too much of it. We cannot continue with business as usual," he said.

But what did the Romans to do make their concrete so durable without the modern technologies available today?

They used volcanic ash mixed with as a binding agent. The not-so-secret recipe was documented around 30 B.C. by Marcus Vitruvius Pollio, an engineer for Octavian, who became Emperor Augustus.

Some success in green concrete making has been seen with fly ash, a byproduct of industrial coal plants. But fly ash is not overly abundant enough to made a dent in the world's concrete needs.

 "Volcanic ash is available in a good deal of the world, usually there are entire mountains of it following a volcanic eruption," Monteiro said. "The Romans were unbelievably good at using it as a building material."

The ancient formula takes a long time to dry, however, and wouldn't  be suitable for building bridges or dams. But ancient Roman concrete's longevity has obvious benefits.

"They wanted a concrete that could last forever," Monteiro said to U.S. News & Word Report. "They were practical and good engineers, and from the ruins you can see it has long-term durability."