6 lines · 87 words · 0:34 read aloud
The Concrete That Heals Itself
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Modern concrete cracks and crumbles within decades. Some Roman concrete has lasted two thousand years.
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For a long time, nobody knew exactly why.
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Then in 2023, researchers at MIT looked closely at small white lumps in the concrete, called lime clasts.
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They found the Romans likely mixed in quicklime while hot. It left pockets of calcium inside.
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When a crack lets water in, that calcium dissolves and hardens again, sealing the crack.
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That's part of why the Pantheon's dome in Rome still stands, nearly nineteen centuries later.
