ROME, Italy – The ancient Romans were renowned for their mastery of building and engineering, with the aqueducts serving as one of their most famous achievements. These still-functional marvels rely on a unique construction material: pozzolanic concrete, a remarkably durable substance that gave Roman structures their incredible strength.
One of the most well-preserved Roman structures is the Pantheon, nearly 2,000 years old and still boasting the world’s largest dome of unreinforced concrete.
For years, the exceptional properties of Roman concrete were believed to be attributed to pozzolana, a volcanic ash mix named after the Italian city of Pozzuoli, and lime. When mixed with water, these materials react to produce strong concrete. However, an international team of researchers led by Massachusetts Institute of Technology (MIT) discovered in 2023 that there is more to the story.
The team, led by MIT civil engineer Linda Seymour and materials scientist Admir Masic, studied 2,000-year-old samples of Roman concrete from the archaeological site of Privernum in Italy. Through their analysis, they found that the lime clasts in the concrete were not consistent with standard methods of pozzolanic concrete production. Instead, they concluded that Roman concrete was likely made by mixing quicklime directly with pozzolana and water at extremely high temperatures, a process they coined as “hot mixing.”
This revelation not only sheds new light on ancient Roman construction methods but also opens the door to potential advancements in modern construction techniques. The hot mixing method produces high-temperature-associated compounds that would not otherwise form, resulting in a concrete with remarkable self-healing abilities.
The unique properties of Roman concrete, including its remarkable self-healing abilities, have been observed in concrete from other ancient sites as well. The team’s experiments with ancient and modern recipes using quicklime confirmed that concrete made with this method was fully healed within two weeks of cracking, while control concrete remained cracked.
These findings offer potential for more durable and environmentally friendly alternatives to current concretes, with implications for the longevity of construction materials and the durability of 3D-printed concrete formulations.
The research, published in Science Advances, presents an exciting opportunity for the construction industry to explore new possibilities in creating stronger and more sustainable concrete formulations for the future.