Scientists have discovered the formula for Roman concrete, which is far superior to modern concrete. While modern concrete can degrade in as little as 50 years, many Roman structures built thousands of years ago remain standing. A study in 2023 revealed that the Romans used more than just seawater in their concrete, specifically quicklime. When mixed with seawater, quicklime produces a hot chemical reaction and leaves chunks of undissolved lime throughout the mixture. This creates a self-healing concrete, which can repair itself when it cracks, as rainwater reacts with the lime chunks and fills the gaps. In 2021, cement production accounted for 8% of greenhouse gas emissions, so a self-healing concrete could reduce emissions by eliminating the need to constantly repave.