6 lines · 94 words · 0:34 read aloud
Why Roman Concrete Gets Stronger With Age
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Some Roman harbors have stood in seawater for two thousand years. Modern concrete can crack in decades.
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The Romans mixed volcanic ash with lime, and they didn't always mix it evenly.
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Researchers found small white lumps of lime scattered through their concrete, long thought to be mistakes.
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It turns out those lumps help heal cracks. When water gets in, the lime dissolves and forms new mineral.
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In seawater, the ash reacts over time and grows new crystals inside the stone.
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So the Romans weren't just building walls. They were building walls that repaired themselves.
