DNA Explainer: All about 'self healing concrete', that makes ancient monuments durable for centuries

We have all marveled at the Roman temple of Pantheon and the Column of Phocas, which have been standing tall for centuries without any significant damage or cracks, which is not the case with several modern-day buildings, which are just decades old.

One of the most notable and mesmerizing monuments across the world is the Roman temple of Pantheon, which was constructed in 128 AD and still stands intact, without any damage. Pantheon has the world’s largest dome which was made with unreinforced concrete.

The magic behind the construction of such monuments is the manufacturing strategies by the Romans and the ‘self-healing’ concrete which doesn’t get cracks or gaps, even after thousands of years. Here is why ancient monuments have been surviving for centuries across the world.

What is ‘self-healing’ concrete, used to build monuments?

The secret behind the self-healing concrete used for making ancient monuments last has been uncovered by a team led by researchers from the Massachusetts Institute of Technology (MIT), who determined how Roman monuments are lasting this long without damage.

The researchers from MIT detected several self-healing features that the artists and workers had incorporated into the concrete, made to build the Roman structures.

Earlier, researchers had identified that the reason why the concrete is durable is because of the pozzolanic material, or volcanic ash that was brought from Pozzuoli, in the Bay of Naples. Now, they have also identified small, distinctive, millimeter-scale bright white mineral features in the samples.

One of the most common components in making the concrete durable and strong is lime, which also gave the monuments a self-healing capacity in the longer run.

As quoted by India Today, the author of the MIT paper said, “If the Romans put so much effort into making an outstanding construction material, following all of the detailed recipes that had been optimized over the course of many centuries, why would they put so little effort into ensuring the production of a well-mixed final product? There has to be more to this story.”

Earlier, it was believed that Romans used a paste of lime and water to make the monuments. Now, researchers have determined that the white inclusions were made out of various forms of calcium carbonate, which were subjected to high temperatures and then made to react with quicklime.

The MIT researcher said, “The benefits of hot mixing are twofold: First, when the overall concrete is heated to high temperatures, it allows chemistries that are not possible if you only used slaked lime, producing high-temperature-associated compounds that would not otherwise form. Second, this increased temperature significantly reduces curing and setting times since all the reactions are accelerated, allowing for much faster construction.”

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