Scientists studying the composition of Roman concrete, which has been submerged under the Mediterranean Sea for the last 2,000 years, have discovered that it was superior to modern-day concrete in terms of durability and being less environmentally damaging.
The Romans made concrete by mixing lime and volcanic rock. For underwater structures, the combination of lime and volcanic ash with seawater instantly triggered a chemical reaction in which the lime incorporated molecules into its structure and reacted with the ash to cement the whole mixture together.
The team of researchers found that Roman concrete differs from the modern kind in several essential ways. One is the kind of glue that binds the concrete’s components together. Roman concrete produces a significantly different compound to modern day Portland cement, which is an incredibly stable binder. The second concerns the hydration products in concrete – the ancient seawater concrete contains the ideal crystalline structure of Tobermorite, which has a greater strength and durability than the modern equivalent.
Finally, microscopic studies identified other minerals in the ancient concrete which show potential application for high-performance concretes, including the encapsulation of hazardous wastes.
The results of the study show how these improvements could be adopted in the modern world and, in particular, how they could result in a significant reduction of environmental damage caused by the manufacturing of concrete.