We Finally Know Why Ancient Roman Concrete Stood The Test of Time

The ancient Romans were masters of building and engineering, perhaps most famously represented by the aqueducts . Those still-functional marvels rely on a unique construction material: pozzolanic concrete, a spectacularly durable mix that gave Roman structures their incredible strength.

Even today, one of their masterpieces – the Pantheon in Rome, still intact and nearly 2,000 years old – holds the record for the world's largest dome of unreinforced concrete.

The remarkable properties have generally been attributed to its ingredients: pozzolana – a mix of volcanic ash named after the Italian city of Pozzuoli, where a significant deposit is found – and lime . The two materials react with water to produce strong, long-lasting concrete.

But it turns out that's not the whole story.