Scientists have finally solved some mysteries surrounding ancient Roman concrete and its incredible "self-healing" properties.
The ancient Romans were many great things. They were disciplined soldiers, explorers, traders, but perhaps, above all, innovators and masters of engineering. They constructed a vast network of roads, aqueducts, massive temples, and other structures. And even though these buildings were erected in antiquity, many remain standing to this date. Their secret? Ancient Roman concrete. Rome’s famous Pantheon was one of the most famous structures built from this material. This structure is considered the world’s largest unreinforced concrete dome. It opened in 128 Ano Domini and remains “intact,” as well as countless other structures built in Rome.
Modern structures, built with what many consider a far better material, have collapsed after a few decades. So, how much better was ancient Roman concrete? The answer: much better than many would imagine. Scientists have worked for decades in an attempt to crack the secrets of ancient Roman concrete and unveil its formula. Their interest focused on structures exposed to harsh conditions, such as piers, culverts, or any other structure built on seismically active land.
Secrets of Ancient Roman Concrete
Researchers from MIT, Harvard University, and labs in Italy and Switzerland have advanced this field in the last few years. Scientists have revealed ancient concrete-making strategies that incorporated several key self-healing functionalities. The findings are published in the journal Science Advances in a paper by MIT professor of civil and environmental engineering Admir Masic, former doctoral student Linda Seymour, and four other experts.
It was assumed that the key to the incredible durability of ancient Roman concrete was based on one main ingredient: pozzolanic material, like volcanic ash from the Pozzuoli area of Naples. It is known throughout history that this material was shipped across the Roman empire and was used in the construction of structures. It was described and mentioned by writers and architects of antiquity as a key ingredient for concrete production.
A closer view
A close examination of ancient Roman concrete revealed small distinctive white mineral features. These have long been recognized as a component of Roman concrete. The white millimetric pieces, often referred to by experts as lime clasts, originate from lime. This is another key component of ancient concrete. Curiously, this millimetric material had previously been dismissed as no more than sloppy mixing practices or poor-quality materials. But the new study suggests otherwise. It offers evidence that the tiny clasts of lime gave ancient Roman concrete a previously unknown “self-healing- capability.