The ancient Romans were masters of engineering, constructing vast networks of roads, aqueducts, ports and buildings whose remains have survived for two millennia. Many of these structures were built with concrete. Rome’s famed Pantheon, which features the world’s largest unreinforced concrete dome, for example, was dedicated in A.D. 128 and is still intact today, while some ancient Roman aqueducts continue to deliver water to the Italian capital.
For many years, researchers have assumed that the key to Roman concrete’s durability was based on one ingredient: pozzolanic material such as volcanic ash from the area of Pozzuoli, on the Bay of Naples. But now, a team of investigators from MIT, Harvard University and laboratories in Italy and Switzerland has discovered ancient concrete-manufacturing strategies that incorporated several key self-healing functionalities.
Published in the journal Science Advances, their findings reveal that, in addition to ash, the concrete contains “lime clasts”—tiny white chunks that originate from lime.
Previously disregarded as evidence of sloppy mixing practices or poor-quality materials, the new study suggests that lime clasts actually gave the concrete self-healing capabilities. The research team is now working to commercialize a modified cement product made with these materials.
