Scientists study ancient Roman and Mayan buildings to improve modern architecture

Ancient builders around the world created structures that still stand thousands of years later—from Roman engineers pouring thick concrete sea barriers, to Mayan masons crafting plaster sculptures of gods, to building structures to ward off invaders Chinese builders of city walls.

However, many newer buildings have begun to shorten their lifespan: the concrete that makes up most of the modern world has a lifespan of about 50 to 100 years. A growing number of scientists have been studying materials from long-ago eras — hacking away at chunks of buildings, studying historical texts, mixing imitated recipes — in hopes of uncovering how they have been preserved over thousands of years.

This reverse engineering uncovered a surprising array of ingredients mixed into the old building, including bark, volcanic ash, rice, beer, and even urine. These unexpected additions could be the key to some impressive properties, such as getting stronger over time and the ability to “heal” cracks as they form.

Figuring out how to replicate these characteristics could have real consequences today: While our modern concrete has the ability to support massive skyscrapers and heavy infrastructure, it can’t compete with the durability of these ancient materials.

As the threat of climate change intensifies, there are growing calls to make buildings more sustainable. A a recent report It is estimated that the built environment is responsible for more than one-third of global CO2 emissions, with cement production alone accounting for more than 7% of this.

Carlos Rodriguez-Navarro, the conservator of cultural heritage, said: “If you improve the properties of the material by using…the traditional recipes of the Mayans or the ancient Chinese, you can make them more A sustainable way to produce materials that can be used in modern construction.” Researcher at the University of Granada, Spain.

AP Photo/Domenico Stinelis

ancient roman concrete

Many researchers look to the Romans for inspiration. Beginning around 200 BC, architects from the Roman Empire began constructing impressive concrete structures that have withstood the test of time—from the towering dome of the Pantheon to the sturdy aqueducts that still carry water today.

John Oleson, an archaeologist at the University of Victoria in Canada, said that even in ports where sea water has long eroded buildings, you will find that the concrete “is basically the same as when it was poured 2,000 years ago.”

Most modern concrete starts with Portland cement, a powder made by heating limestone and clay to extremely high temperatures and grinding them. This cement is mixed with water to form a chemically reactive paste. Then, larger materials like rocks and gravel are added, and the cement slurry binds them into concrete blocks.

A similar process occurred in Rome, as recorded by ancient architects such as Vitruvius. Ancient builders mixed materials like charred limestone and volcanic sand with water and gravel, creating a chemical reaction that glued everything together.

Now, scientists think they have discovered the key reason why some Roman concrete was able to hold up buildings for thousands of years: the ancient material has an unusual ability to repair itself. Exactly how this happens is unclear, but scientists are starting to look for clues.

in a study Admir Masic, a civil and environmental engineer at MIT, proposed in a paper published earlier this year that the energy came from lumps of lime spread throughout the Roman material, rather than being evenly mixed. Researchers used to think the fragments showed the Romans didn’t mix their materials enough.

Instead, after analyzing specific samples from the ancient city of Privernum outside Rome, scientists found that the blocks enhance the material’s “self-healing” ability. Masich explained that when cracks form, water can seep into the concrete. This water activates the remaining lime bags, triggering new chemical reactions that fill in the damaged areas.

Mary Jackson, a geologist at the University of Utah, sees it differently.she Research The key to the discovery may lie in the specific volcanic materials used by the Romans.

Builders collect volcanic rock left over from volcanic eruptions and mix it into concrete. This naturally reactive material changes over time as it interacts with the elements, allowing it to seal cracks that form, Jackson said.

The ability to adapt over time “is really the genius of the material,” Jackson said. “Concrete is designed very well to be self-sustaining.”

tree “juice”

At the Mayan ruins of Copán in Honduras, intricate lime sculptures and temples remain intact even after being exposed to hot and humid conditions for more than 1,000 years.and according to a Research published earlier this yearthe secret to the longevity of these structures may lie in the trees that sprout between them.

Rodriguez-Navarro, who worked on the study, explains that the researchers here have close ties to the creators of these structures: they met with local masons in Honduras who can trace their lineage back to the Mayan builders.

AP Photo/Moises Castillo

Masons recommend using extracts of the local Chukum and Geot trees in the lime mixture. When the researchers tested the recipe—collecting the bark, placing the chunks in water, and then adding the resulting tree “sap” to the material—they found that the resulting plaster was particularly durable against physical and chemical damage.

When the scientists zoomed in, they saw that some of the organic matter in the sap was incorporated into the molecular structure of the gypsum. In this way, Mayan plaster is able to imitate strong natural structures like shells and sea urchin spines and borrow some of their toughness, Rodriguez-Navarro said.

The study found that a variety of natural materials were mixed into the structure long ago: fruit extracts, milk, cheese curds, beer, and even feces and urine.The mortar that holds together some of China’s most famous buildings, including the Great Wall and Forbidden City, includes Trace amounts of starch in glutinous rice.

Luck or skill?

Cecilia Pace, a materials scientist at the University of Sheffield in the United Kingdom, says some of these ancient builders may have just been lucky. They’ll add anything to their mix as long as it’s cheap and available, and the stuff that doesn’t work has long since gone out of business.

“They’re going to put all kinds of stuff into the construction,” Pace said. “Now, we only have surviving buildings left. So it’s like a natural selection process.”

But Thirumalini Selvaraj, a civil engineer and professor at the Indian Institute of Technology Vellore, said some materials seemed to show more intention, such as in India where builders mixed local materials into Different performance.

In humid areas of India, builders use local herbs to help buildings cope with moisture, according to Selvaraj’s research. In coastal areas, they add jaggery, an unrefined sugar that helps prevent salt damage. In areas with a higher risk of earthquakes, they used ultra-light “floating bricks” made from rice husks.

“They know the area, they know the soil conditions, they know the climate,” Selvaraj said. “So they designed a material based on that.”

ancient roman style skyscraper

Today’s builders can’t just copy ancient recipes. Although Roman concrete lasted a long time, it couldn’t withstand heavy loads: “You couldn’t build a modern skyscraper with Roman concrete,” Olson said. “When you get to the third level, it collapses.”

Instead, researchers are trying to add some of the properties of ancient materials to the modern mix. Masic is part of a new startup trying to use Roman-style “self-healing” concrete to build new projects. Jackson is working with the Army Corps of Engineers to design concrete structures that can hold up well in seawater, such as those in Roman ports, to help protect shorelines from rising sea levels.

Masic says we don’t need to let things go on for a long time like the Romans did to have an impact. If we extend the life of concrete by 50 or 100 years, “we’ll need less demolition, maintenance and materials in the long run.”