Some Roman structures have stood for 2,000 years, even in seawater. A 2023 study found small lumps of lime in the concrete. When water seeps into a crack, they dissolve and seal it.
Truth label: Established. Strong evidence and broad agreement among experts.
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Hot mixing
Researchers think Romans mixed quicklime in hot, which left those lime lumps behind rather than a smooth mix.
Stronger with the sea
In harbour walls, seawater reacts with volcanic ash in the mix to grow new minerals that make it tougher over time.
Learn
- The Pantheon. Its dome in Rome is still the largest unreinforced concrete dome in the world, nearly 1,900 years later.
Test yourself
What helps Roman concrete seal cracks?
Lumps of lime. Lime lumps dissolve in water and fill the crack.
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