How ancient Roman concrete could impact tomorrow’s climate

Nowadays, all roads may not lead to Rome. But they could soon all be built using newly discovered techniques that first appeared in the ancient city.

Researchers are aiming to unravel the secrets of ancient Roman concrete – which has consistently survived for millennia in harsh environments – and integrate them into the modern version, in a bid to improve its climate impact and durability.

Background: Modern concrete, developed in England in the 19th century, is the second-most-used substance in the world behind water, and the world’s most popular building material by far, with its ton-for-ton usage coming in 2x higher than steel, wood, plastics, and aluminum combined.

• The material is cheap, strong, and standardized – but also much less resilient than the Roman concrete of old.
• Over the course of decades, modern concrete typically develops cracks that can eventually destroy the material by letting in water.

But with the Roman version of concrete, cracks and water make the material stronger. That’s due to visible white chunks within the limestone, called “clasts,” which scientists previously believed were unintentional products of poor craftsmanship.

However, according to research by MIT chemist Dr. Admir Masic and others, the ancient Romans intentionally built the clasts (made of calcium) into their concrete to help seal any cracks and make the concrete self-healing.

How it works:

• As cracks form, water seeps in and dissolves the calcium clasts in the lime, which then form into solid calcium carbonate – essentially creating new rock that fills in the old cracks.
• In field tests involving modern analogues of ancient Roman concrete, researchers found that creating cracks in the material and submerging it in water for nearly a year actually causes the structure to become 2x-3x stronger.

💥 The potential impact: Scientists investigating ancient Roman practices are aiming to reduce the carbon footprint of the concrete industry, which is responsible for ~8% of global CO2 emissions. Researchers say adding self-healing properties to modern concrete would reduce overall demand and bring down emissions.