Discovering the secret that helped Roman concrete last thousands of years

(Dan Tri) - Without modern technology, ancient Roman structures still stand firm for more than 2,000 years.

Self-healing concrete

Concrete is the core material of most modern construction. But compared to the incredible durability of ancient monuments like the Colosseum or the Pantheon, today’s concrete has a much shorter lifespan and is in constant need of repair. What makes the difference?

A new study from the Massachusetts Institute of Technology (MIT, USA) has revealed the secret hidden deep inside ancient Roman concrete blocks. It is the ability to self-heal, a feature that seems only to exist in science fiction.

The Roman Colosseum still stands after millennia. (Photo: Archdaily).

The research team analyzed concrete samples taken from the ruins of the ancient city wall in Privernum (Italy). The results showed that although the main ingredients were still familiar materials such as pozzolana volcanic ash, tuff and lime, small white crystals appeared inside, which were previously thought to be "mixing errors".

In fact, it is the lime itself that is the key. When the concrete cracks and water seeps in, the unreacted lime flakes immediately trigger a chemical process, creating a saturated calcium solution.

This solution then crystallizes into calcium carbonate, a compound that can fill cracks and re-bond surrounding material particles. In this way, the concrete “patches” its structure without human intervention.

This reaction is completely natural, similar to the way the human body heals wounds on the skin. According to the research team, this is a very rare feature in construction materials: a “chemical self-healing” mechanism.

Different way of production

Another big difference was the technique used to make the concrete. Instead of using slaked lime (lime mixed with water), the Romans may have used a hot-mixing technique. They added quicklime directly to the mixture of aggregate and pozzolana ash, and then added water.

This magnified image shows calcium aluminosilicate (CASH) cementitious material formed when volcanic ash and lime react with seawater. Platinum crystals of Al-tobermorite have grown within the CASH cementitious matrix (Photo: Getty).

The thermal reaction generated from this process creates undecomposed lime fragments that act as calcium reserves.

After dozens or even hundreds of years, when the concrete block cracks due to climate, earthquakes or loads, these calcium stores are activated, creating a self-healing chain reaction.

This discovery not only helps explain why Roman structures have endured for millennia, but also opens up new directions for the modern construction materials industry.

Professor Admir Masic – head of the research team at MIT – said that if this self-healing technology is recreated and applied to modern concrete, we can extend the life of buildings, significantly reduce repair costs and most importantly, reduce greenhouse gas emissions.

The cement industry is currently responsible for about 8% of global carbon emissions, largely due to the production, transportation, and maintenance of buildings. Developing self-healing concrete, like the ancient Romans, could help change this situation.

Without the need for super-advanced materials or complex industrial chains, ancient techniques are still showing their timeless power. And sometimes, to move forward, humanity is forced to look back at what our ancestors left behind.

Source: https://dantri.com.vn/khoa-hoc/phat-hien-bi-mat-giup-be-tong-la-ma-ben-hang-nghin-nam-20250728070224281.htm