Hank: Scientists just reverse engineered the formula for Roman concrete, and it is way better than the modern stuff. While today's concrete can degrade in as little as 50 years, plenty of Roman structures that were built thousands of years ago are still going strong.

A few years ago, we learned that mixing concrete with seawater instead of freshwater was part of the Romans' secret, but a 2023 study found that wasn't the only trick of their sleeves. If they had sleeves, which they didn't, because they had togas.

The Roman concrete recipe calls for a mineral called quicklime. When mixed with seawater, quicklime produces a hot chemical reaction and leaves chunks of undissolved lime throughout the mixture. This produces concrete that can repair itself. When it cracks, rain water leaks in and hits those lime chunks, which reactivates the cement and fills the gaps as they form.

In 2021, cement production accounted for 8% of greenhouse gas emissions, so a self-healing concrete could help us cut emissions by eliminating the need to repave stuff all the time.

[end]