Ancient Manufacturing Technique Unlocks the Secret to Long-Lasting Concrete

Researchers from MIT, Harvard University, and laboratories in Italy and Switzerland have discovered ancient concrete-manufacturing strategies used by the ancient Romans that incorporated several key self-healing functionalities.

The new study suggests that tiny lime clasts gave the concrete a previously unrecognised self-healing capability. The researchers found that during the hot mixing process, the lime clasts developed a characteristically brittle nanoparticulate architecture, creating an easily fractured and reactive calcium source.

As soon as tiny cracks start to form within the concrete, they can preferentially travel through the high-surface-area lime clasts. This material can then react with water, creating a calcium-saturated solution, which can recrystallise as calcium carbonate and quickly fill the crack, or react with pozzolanic materials to further strengthen the composite material. These reactions take place spontaneously and therefore automatically heal the cracks before they spread.

The team produced samples of hot-mixed concrete that incorporated both ancient and modern formulations, deliberately cracked them, and then ran water through the cracks to prove the mechanism responsible for the durability of the Roman concrete.

The results showed that the cracks healed within two weeks. The team is now working to commercialise this modified cement material to expand the service life of concrete materials and reduce the environmental impact of cement production.

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