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2.000-Year-Old Roman Concrete: Durability, Self-Healing, and a Secret That Could Transform Modern Construction
The ancient Romans dominated the engineering like few others. Proof of this are its aqueducts, roads and monuments that have survived millennia practically intact. But what was the secret behind this durability? The answer may lie in a special type of Roman concrete: pozzolanic.
The best example of the strength of this material is the Pantheon in Rome. Built almost 2.000 years ago, it still boasts the largest unreinforced concrete dome in the world. Structures like this have defied time and intrigued scientists for decades.
The known formula for Roman concrete involves two main ingredients: pozzolan, a mixture of volcanic ash, and lime. This combination creates an extremely durable material, but a recent study suggests there’s more to this secret than previously thought.
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Unexpected discovery
In 2023, researchers at the Massachusetts Institute of Technology (MIT) analyzed samples of Roman concrete from the Privernum site in Italy. What caught the team's attention were small pieces of lime scattered throughout the material.
These fragments have been seen before, but were thought to be a defect in the mixture. However, MIT scientist Admir Masic questioned this explanation.
"If the Romans went to such great lengths to make an exceptional building material, following all the detailed recipes that had been optimized over many centuries, why would they put so little effort into ensuring that they produced a well-mixed final product? There has to be more to the story.", Masic said at the time.
The answer was in the way concrete was made. Instead of just mixing slaked lime with pozzolan and water, the Romans added quicklime directly to the mix, raising the temperatures of the event.
The process, called “hot mixing,” created the lime fragments and brought unexpected benefits.
Amazing advantages
The first benefit is chemical. Extreme heat causes reactions that do not occur at normal temperatures, creating more resistant compounds. In addition, the process speeds up the curing of concrete, allowing for faster construction.
But the most impressive thing is the ability to “self-healing” of the material. When Roman concrete cracks, water enters the crack and dissolves the lime fragments. This calcium-rich solution reacts with the environment, forming calcium carbonate, which fills and seals the crack naturally.
This feature has previously been observed in the Tomb of Cecilia Metella, another 2.000-year-old structure. There, researchers noted that the cracks had been sealed with calcite over the centuries, maintaining the integrity of the monument.
Tests confirm resistance
To prove their discovery, the scientists recreated Roman concrete using the same technique and compared it with a version without quicklime. In cracking tests, the traditional concrete was found to crack, while the Roman concrete completely regenerated in just two weeks.
This effect may explain why Roman walls withstood the impact of sea waves for so long, while modern concrete walls tend to deteriorate quickly.
Now, a team at MIT is working to adapt this technique to the modern world. In addition to creating stronger buildings, pozzolanic concrete could be a more sustainable alternative, reducing the need for repairs and avoiding emissions from the construction industry.
"It’s exciting to think about how these more durable concrete formulations could expand not only the lifespan of these materials, but also how they could improve the durability of 3D printed concrete formulations.“, said Masic.
With information sciencealert.
Because we don't use Roman concrete in residential constructions at least, I believe that low-income housing would even be cheaper.
I question the resistance and whether the inclusion of steel bars, in what we call reinforced concrete, is the difference in the durability of reinforced concrete and Roman concrete parts.
I would really like to be able to use this technique in my Cuba productions and develop Sculpture with them.