In 2023, scientists from MIT made an exciting discovery about Roman concrete. They found that the ancient Romans used a technique called “hot mixing” with quicklime, which allowed their concrete to heal itself. Recent studies confirmed this technique, now documented in a paper published in Nature Communications.
Roman concrete was different from what we use today. While modern concrete often includes Portland cement, Roman concrete combined a semi-liquid mortar with larger pieces of stone or brick. Portland cement is made by heating limestone and clay, then grinding it to a fine powder. In contrast, Roman concrete used fist-sized aggregates and special volcanic materials.
The Roman architect Vitruvius, writing around 30 CE, described methods for making concrete walls that could last for ages. He suggested walls be at least two feet thick and made from materials like red stone, brick, or even volcanic rock. These materials were mixed with lime and volcanic ash.
Admir Masic, an environmental engineer at MIT, has been studying Roman concrete for years. In previous research, he developed innovative tools to analyze concrete samples, such as Raman spectroscopy and energy dispersive spectroscopy. His team investigated the concrete from the ancient Tomb of Caecilia Metella, shedding light on how Romans achieved such durability.
In recent studies, Masic and his team looked at the concrete from Privernum, focusing on mysterious white mineral chunks called “lime clasts.” Initially thought to be a sign of poor mixing, Masic’s research revealed that these clasts were part of a sophisticated design. When cracks form, they guide moisture to the lime clasts, which react to repair the material. This self-healing trait is one reason why Roman structures have lasted for centuries.
Interestingly, studies show that about 30% of historical buildings worldwide still use Roman concrete techniques, emphasizing its resilience. Experts believe that understanding these ancient methods could inspire more sustainable building practices today. As we face modern challenges in construction and durability, looking back can often reveal solutions for the future.
For those interested in learning more about ancient building techniques, you can read about them in Vitruvius’s De architectura or explore academic studies on the topic here.
